<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019e280b-34ad-7471-9414-8b374ac38f8b,g:bb5ff7e3-b935-4952-b9a7-0a37de7f3a49-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="https://xbrl.org/2023/arcrole/summation-item" xlink:type="simple" xlink:href="https://www.xbrl.org/2023/calculation-1.1.xsd#summation-item"/>
  <link:roleRef roleURI="http://fastly.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETS" xlink:type="simple" xlink:href="fsly-20260630.xsd#CONDENSEDCONSOLIDATEDBALANCESHEETS"/>
  <link:calculationLink xlink:role="http://fastly.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETS" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_019e280b-3578-73e8-a6d9-5f0a71ff490c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Assets"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_019e280b-3578-72e9-894f-d98a48066bd1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseRightOfUseAsset"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019e280b-3578-73e8-a6d9-5f0a71ff490c" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_019e280b-3578-72e9-894f-d98a48066bd1" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrent_019e280b-3578-79a7-8ee9-fabab28b906e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetsCurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019e280b-3578-73e8-a6d9-5f0a71ff490c" xlink:to="loc_us-gaap_AssetsCurrent_019e280b-3578-79a7-8ee9-fabab28b906e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_019e280b-3578-7ba2-8097-b26d2f8e4713" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherAssetsNoncurrent"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019e280b-3578-73e8-a6d9-5f0a71ff490c" xlink:to="loc_us-gaap_OtherAssetsNoncurrent_019e280b-3578-7ba2-8097-b26d2f8e4713" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_019e280b-3578-7b7d-a946-c39269f0a4d7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019e280b-3578-73e8-a6d9-5f0a71ff490c" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_019e280b-3578-7b7d-a946-c39269f0a4d7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization_019e280b-3578-7682-a3e2-2819e844ea45" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019e280b-3578-73e8-a6d9-5f0a71ff490c" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization_019e280b-3578-7682-a3e2-2819e844ea45" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_019e280b-3578-79e9-8606-44e48b57070e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Goodwill"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019e280b-3578-73e8-a6d9-5f0a71ff490c" xlink:to="loc_us-gaap_Goodwill_019e280b-3578-79e9-8606-44e48b57070e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_019e280b-3578-76c5-82d7-3c0bead4f6b8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Liabilities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_019e280b-3578-7fc5-9ef0-cc57f0bc7958" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseLiabilityNoncurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019e280b-3578-76c5-82d7-3c0bead4f6b8" xlink:to="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_019e280b-3578-7fc5-9ef0-cc57f0bc7958" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrent_019e280b-3578-7c7c-a34d-c2df7a03e79e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesCurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019e280b-3578-76c5-82d7-3c0bead4f6b8" xlink:to="loc_us-gaap_LiabilitiesCurrent_019e280b-3578-7c7c-a34d-c2df7a03e79e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesNoncurrent_019e280b-3578-736a-adf1-db7704632789" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherLiabilitiesNoncurrent"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019e280b-3578-76c5-82d7-3c0bead4f6b8" xlink:to="loc_us-gaap_OtherLiabilitiesNoncurrent_019e280b-3578-736a-adf1-db7704632789" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_019e280b-3578-7a83-b02c-ed0567fe39b2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019e280b-3578-76c5-82d7-3c0bead4f6b8" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_019e280b-3578-7a83-b02c-ed0567fe39b2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrent_019e280b-3578-7f67-a402-fd10660074a6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesCurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableCurrent_019e280b-3578-7e40-a4f6-8d16bc33ca4d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccountsPayableCurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_019e280b-3578-7f67-a402-fd10660074a6" xlink:to="loc_us-gaap_AccountsPayableCurrent_019e280b-3578-7e40-a4f6-8d16bc33ca4d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedLiabilitiesCurrent_019e280b-3578-71be-acae-050dc791663b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccruedLiabilitiesCurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_019e280b-3578-7f67-a402-fd10660074a6" xlink:to="loc_us-gaap_AccruedLiabilitiesCurrent_019e280b-3578-71be-acae-050dc791663b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtCurrent_019e280b-3578-7634-9774-6c4f0516a358" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebtCurrent"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_019e280b-3578-7f67-a402-fd10660074a6" xlink:to="loc_us-gaap_LongTermDebtCurrent_019e280b-3578-7634-9774-6c4f0516a358" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityCurrent_019e280b-3578-7d40-aa68-413491189967" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseLiabilityCurrent"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_019e280b-3578-7f67-a402-fd10660074a6" xlink:to="loc_us-gaap_OperatingLeaseLiabilityCurrent_019e280b-3578-7d40-aa68-413491189967" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityCurrent_019e280b-3578-716c-accf-4ded19571420" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ContractWithCustomerLiabilityCurrent"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_019e280b-3578-7f67-a402-fd10660074a6" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityCurrent_019e280b-3578-716c-accf-4ded19571420" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesCurrent_019e280b-3578-7256-a733-cd86512f3f41" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherLiabilitiesCurrent"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_019e280b-3578-7f67-a402-fd10660074a6" xlink:to="loc_us-gaap_OtherLiabilitiesCurrent_019e280b-3578-7256-a733-cd86512f3f41" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019e280b-3578-76fb-affa-1ae0c4c6bd04" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValue_019e280b-3578-747a-a6b5-d546048d5418" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockValue"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_019e280b-3578-76fb-affa-1ae0c4c6bd04" xlink:to="loc_us-gaap_CommonStockValue_019e280b-3578-747a-a6b5-d546048d5418" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapital_019e280b-3578-74aa-82f6-f62db3d46ace" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdditionalPaidInCapital"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_019e280b-3578-76fb-affa-1ae0c4c6bd04" xlink:to="loc_us-gaap_AdditionalPaidInCapital_019e280b-3578-74aa-82f6-f62db3d46ace" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_019e280b-3578-7591-93ba-ed026980f8f2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_019e280b-3578-76fb-affa-1ae0c4c6bd04" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_019e280b-3578-7591-93ba-ed026980f8f2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_019e280b-3578-7788-8fe0-537f55a5eb00" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_019e280b-3578-76fb-affa-1ae0c4c6bd04" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_019e280b-3578-7788-8fe0-537f55a5eb00" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_019e280b-3578-7e46-adc1-3168ccd94f16" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_019e280b-3578-7d7a-ae3b-f4e0a90dc3a1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Liabilities"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquity_019e280b-3578-7e46-adc1-3168ccd94f16" xlink:to="loc_us-gaap_Liabilities_019e280b-3578-7d7a-ae3b-f4e0a90dc3a1" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingencies_019e280b-3578-7a17-9b15-652f9c12a2f5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommitmentsAndContingencies"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquity_019e280b-3578-7e46-adc1-3168ccd94f16" xlink:to="loc_us-gaap_CommitmentsAndContingencies_019e280b-3578-7a17-9b15-652f9c12a2f5" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019e280b-3578-77b2-9cc0-670aeed5831e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquity"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquity_019e280b-3578-7e46-adc1-3168ccd94f16" xlink:to="loc_us-gaap_StockholdersEquity_019e280b-3578-77b2-9cc0-670aeed5831e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrent_019e280b-3578-7dac-92a2-6e45d13125f8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetsCurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019e280b-3578-75fc-ae85-95850c26455d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_019e280b-3578-7dac-92a2-6e45d13125f8" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019e280b-3578-75fc-ae85-95850c26455d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketableSecuritiesCurrent_019e280b-3578-78f9-8330-071c170f4c7c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MarketableSecuritiesCurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_019e280b-3578-7dac-92a2-6e45d13125f8" xlink:to="loc_us-gaap_MarketableSecuritiesCurrent_019e280b-3578-78f9-8330-071c170f4c7c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_019e280b-3578-7c4c-8937-520ae2bb26df" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PrepaidExpenseAndOtherAssetsCurrent"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_019e280b-3578-7dac-92a2-6e45d13125f8" xlink:to="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_019e280b-3578-7c4c-8937-520ae2bb26df" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_019e280b-3578-7aa8-9fc4-1bff643e29ba" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccountsReceivableNetCurrent"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_019e280b-3578-7dac-92a2-6e45d13125f8" xlink:to="loc_us-gaap_AccountsReceivableNetCurrent_019e280b-3578-7aa8-9fc4-1bff643e29ba" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://fastly.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS" xlink:type="simple" xlink:href="fsly-20260630.xsd#CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS"/>
  <link:calculationLink xlink:role="http://fastly.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrossProfit_019e280b-3578-77e2-916c-21229f46d29d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GrossProfit"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_019e280b-3578-724e-bec3-a2dc425ed844" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_GrossProfit_019e280b-3578-77e2-916c-21229f46d29d" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_019e280b-3578-724e-bec3-a2dc425ed844" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfRevenue_019e280b-3578-73d2-95b8-ad08352623f3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CostOfRevenue"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_GrossProfit_019e280b-3578-77e2-916c-21229f46d29d" xlink:to="loc_us-gaap_CostOfRevenue_019e280b-3578-73d2-95b8-ad08352623f3" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_019e280b-3578-7e9f-952b-480ca458722a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrossProfit_019e280b-3579-7744-a0ed-2bde1fd28dd1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GrossProfit"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingIncomeLoss_019e280b-3578-7e9f-952b-480ca458722a" xlink:to="loc_us-gaap_GrossProfit_019e280b-3579-7744-a0ed-2bde1fd28dd1" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpenses_019e280b-3579-7a55-9fe6-06eb2e2ba12e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingExpenses"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingIncomeLoss_019e280b-3578-7e9f-952b-480ca458722a" xlink:to="loc_us-gaap_OperatingExpenses_019e280b-3579-7a55-9fe6-06eb2e2ba12e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpenses_019e280b-3579-76ed-a48a-b21616f30b27" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingExpenses"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpense_019e280b-3579-7c2f-9dc0-c5ad98fc3aa3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ResearchAndDevelopmentExpense"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingExpenses_019e280b-3579-76ed-a48a-b21616f30b27" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpense_019e280b-3579-7c2f-9dc0-c5ad98fc3aa3" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingAndMarketingExpense_019e280b-3579-7750-9d59-8de27b7e29c9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SellingAndMarketingExpense"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingExpenses_019e280b-3579-76ed-a48a-b21616f30b27" xlink:to="loc_us-gaap_SellingAndMarketingExpense_019e280b-3579-7750-9d59-8de27b7e29c9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsly_AssetImpairmentChargesExcludingOperatingLeaseImpairment_019e280b-3579-799f-8d35-d03af846bc82" xlink:href="fsly-20260630.xsd#fsly_AssetImpairmentChargesExcludingOperatingLeaseImpairment"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingExpenses_019e280b-3579-76ed-a48a-b21616f30b27" xlink:to="loc_fsly_AssetImpairmentChargesExcludingOperatingLeaseImpairment_019e280b-3579-799f-8d35-d03af846bc82" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpense_019e8654-6f5e-7950-b2a9-31b2706415d2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GeneralAndAdministrativeExpense"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingExpenses_019e280b-3579-76ed-a48a-b21616f30b27" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpense_019e8654-6f5e-7950-b2a9-31b2706415d2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019e280b-3578-74ac-bdd3-9e71b3b8fd3b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLoss"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019e280b-3578-7b09-ab08-ff01c0dfc7f7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetIncomeLoss_019e280b-3578-74ac-bdd3-9e71b3b8fd3b" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019e280b-3578-7b09-ab08-ff01c0dfc7f7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_019e280b-3578-74f8-9755-6f4bb25c7666" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetIncomeLoss_019e280b-3578-74ac-bdd3-9e71b3b8fd3b" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_019e280b-3578-74f8-9755-6f4bb25c7666" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019e280b-3579-792f-9777-777c4b95254e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_019e280b-3579-7a0a-85d8-aad3620f4d06" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019e280b-3579-792f-9777-777c4b95254e" xlink:to="loc_us-gaap_OperatingIncomeLoss_019e280b-3579-7a0a-85d8-aad3620f4d06" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIncomeInterest_019e280b-3579-73d7-84fa-b512a9867f10" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentIncomeInterest"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019e280b-3579-792f-9777-777c4b95254e" xlink:to="loc_us-gaap_InvestmentIncomeInterest_019e280b-3579-73d7-84fa-b512a9867f10" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseNonoperating_019e280b-3579-7699-952f-66812ec0551d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestExpenseNonoperating"/>
    <link:calculationArc order="3" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019e280b-3579-792f-9777-777c4b95254e" xlink:to="loc_us-gaap_InterestExpenseNonoperating_019e280b-3579-7699-952f-66812ec0551d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_019e280b-3579-76bb-84d8-1b0924e0f422" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019e280b-3579-792f-9777-777c4b95254e" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_019e280b-3579-76bb-84d8-1b0924e0f422" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://fastly.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCOMPREHENSIVELOSS" xlink:type="simple" xlink:href="fsly-20260630.xsd#CONDENSEDCONSOLIDATEDSTATEMENTSOFCOMPREHENSIVELOSS"/>
  <link:calculationLink xlink:role="http://fastly.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCOMPREHENSIVELOSS" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019e280b-3579-7e74-89e5-f9f093349d26" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentNetOfTaxPortionAttributableToParent_019e280b-3579-7fea-aa90-1612b1862be3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentNetOfTaxPortionAttributableToParent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019e280b-3579-7e74-89e5-f9f093349d26" xlink:to="loc_us-gaap_OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentNetOfTaxPortionAttributableToParent_019e280b-3579-7fea-aa90-1612b1862be3" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTax_019e280b-3579-7b7a-b9f6-eb78b2c7c022" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ComprehensiveIncomeNetOfTax"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019e280b-3579-7bd0-b7d4-a8740a72725b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLoss"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTax_019e280b-3579-7b7a-b9f6-eb78b2c7c022" xlink:to="loc_us-gaap_NetIncomeLoss_019e280b-3579-7bd0-b7d4-a8740a72725b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019e280b-3579-7eca-9ebd-32a73b6f6244" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTax_019e280b-3579-7b7a-b9f6-eb78b2c7c022" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019e280b-3579-7eca-9ebd-32a73b6f6244" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://fastly.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCASHFLOWS" xlink:type="simple" xlink:href="fsly-20260630.xsd#CONDENSEDCONSOLIDATEDSTATEMENTSOFCASHFLOWS"/>
  <link:calculationLink xlink:role="http://fastly.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCASHFLOWS" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019e280b-3653-771f-b9c1-6e78f58ca402" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfConvertibleDebt_019e280b-3653-7c5f-aff5-d82e458b2f92" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RepaymentsOfConvertibleDebt"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019e280b-3653-771f-b9c1-6e78f58ca402" xlink:to="loc_us-gaap_RepaymentsOfConvertibleDebt_019e280b-3653-7c5f-aff5-d82e458b2f92" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfDebtIssuanceCosts_019e280b-3653-7d2b-bcfc-aef77a7d7481" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsOfDebtIssuanceCosts"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019e280b-3653-771f-b9c1-6e78f58ca402" xlink:to="loc_us-gaap_PaymentsOfDebtIssuanceCosts_019e280b-3653-7d2b-bcfc-aef77a7d7481" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeasePrincipalPayments_019e280b-3653-7a5d-a051-4cbeae5e6070" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinanceLeasePrincipalPayments"/>
    <link:calculationArc order="3" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019e280b-3653-771f-b9c1-6e78f58ca402" xlink:to="loc_us-gaap_FinanceLeasePrincipalPayments_019e280b-3653-7a5d-a051-4cbeae5e6070" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromStockOptionsExercised_019e280b-3653-7cc4-b746-ea340d4cfafb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromStockOptionsExercised"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019e280b-3653-771f-b9c1-6e78f58ca402" xlink:to="loc_us-gaap_ProceedsFromStockOptionsExercised_019e280b-3653-7cc4-b746-ea340d4cfafb" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromStockPlans_019e280b-3653-72af-94be-c9d377add5d6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromStockPlans"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019e280b-3653-771f-b9c1-6e78f58ca402" xlink:to="loc_us-gaap_ProceedsFromStockPlans_019e280b-3653-72af-94be-c9d377add5d6" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_019e280b-3653-77af-9a29-e02884841780" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e280b-3653-7f2c-b640-97211aa838f9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_019e280b-3653-77af-9a29-e02884841780" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e280b-3653-7f2c-b640-97211aa838f9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019e280b-3653-79ca-97bf-d73fafdc813f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_019e280b-3653-77af-9a29-e02884841780" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019e280b-3653-79ca-97bf-d73fafdc813f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019e280b-3653-7d7b-9ee0-e79009dd459e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_019e280b-3653-77af-9a29-e02884841780" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019e280b-3653-7d7b-9ee0-e79009dd459e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019e280b-3653-788b-b20d-0d8940bbacae" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_019e280b-3653-77af-9a29-e02884841780" xlink:to="loc_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019e280b-3653-788b-b20d-0d8940bbacae" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019e280b-3653-7829-82e9-be1515e5fd27" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireShortTermInvestments_019e280b-3653-75c4-b048-61d6b897217f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsToAcquireShortTermInvestments"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019e280b-3653-7829-82e9-be1515e5fd27" xlink:to="loc_us-gaap_PaymentsToAcquireShortTermInvestments_019e280b-3653-75c4-b048-61d6b897217f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities_019e280b-3653-730d-bb10-1cb03a3ac62c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019e280b-3653-7829-82e9-be1515e5fd27" xlink:to="loc_us-gaap_ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities_019e280b-3653-730d-bb10-1cb03a3ac62c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_019e280b-3653-7f03-a922-7c2078fad7de" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsToAcquirePropertyPlantAndEquipment"/>
    <link:calculationArc order="3" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019e280b-3653-7829-82e9-be1515e5fd27" xlink:to="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_019e280b-3653-7f03-a922-7c2078fad7de" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_019eb122-f6a2-72fc-b60a-5aa74e93bc03" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019e280b-3653-7829-82e9-be1515e5fd27" xlink:to="loc_us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_019eb122-f6a2-72fc-b60a-5aa74e93bc03" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForSoftware_019f11e9-d5e9-77b1-a8a8-c7edbd35668b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsForSoftware"/>
    <link:calculationArc order="5" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019e280b-3653-7829-82e9-be1515e5fd27" xlink:to="loc_us-gaap_PaymentsForSoftware_019f11e9-d5e9-77b1-a8a8-c7edbd35668b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e280b-3653-73cc-b043-3cd6b73aa69a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019e280b-3653-77cc-b95f-3b6b5725b72c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLoss"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e280b-3653-73cc-b043-3cd6b73aa69a" xlink:to="loc_us-gaap_NetIncomeLoss_019e280b-3653-77cc-b95f-3b6b5725b72c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationNonproduction_019e280b-3653-70fb-bb5c-90d88b02399d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DepreciationNonproduction"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e280b-3653-73cc-b043-3cd6b73aa69a" xlink:to="loc_us-gaap_DepreciationNonproduction_019e280b-3653-70fb-bb5c-90d88b02399d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_019e280b-3653-73b9-ac11-131065d2d51e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AmortizationOfIntangibleAssets"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e280b-3653-73cc-b043-3cd6b73aa69a" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_019e280b-3653-73b9-ac11-131065d2d51e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense_019e280b-3653-7a13-bb9d-45141f7e7694" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e280b-3653-73cc-b043-3cd6b73aa69a" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense_019e280b-3653-7a13-bb9d-45141f7e7694" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfFinancingCostsAndDiscounts_019e280b-3653-7e98-9a17-e9bba32c5e66" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AmortizationOfFinancingCostsAndDiscounts"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e280b-3653-73cc-b043-3cd6b73aa69a" xlink:to="loc_us-gaap_AmortizationOfFinancingCostsAndDiscounts_019e280b-3653-7e98-9a17-e9bba32c5e66" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostAmortization_019e280b-3653-7dfa-b9a0-8369e084f04e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CapitalizedContractCostAmortization"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e280b-3653-73cc-b043-3cd6b73aa69a" xlink:to="loc_us-gaap_CapitalizedContractCostAmortization_019e280b-3653-7dfa-b9a0-8369e084f04e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensation_019e280b-3653-75d3-83aa-704d028d993b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensation"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e280b-3653-73cc-b043-3cd6b73aa69a" xlink:to="loc_us-gaap_ShareBasedCompensation_019e280b-3653-75d3-83aa-704d028d993b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_019e280b-3653-7e60-a060-a9f133c5f87c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredIncomeTaxExpenseBenefit"/>
    <link:calculationArc order="8" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e280b-3653-73cc-b043-3cd6b73aa69a" xlink:to="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_019e280b-3653-7e60-a060-a9f133c5f87c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProvisionForDoubtfulAccounts_019e280b-3653-7448-ac3e-d207a7eead8d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProvisionForDoubtfulAccounts"/>
    <link:calculationArc order="9" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e280b-3653-73cc-b043-3cd6b73aa69a" xlink:to="loc_us-gaap_ProvisionForDoubtfulAccounts_019e280b-3653-7448-ac3e-d207a7eead8d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSaleOfPropertyPlantEquipment_019e280b-3653-71e5-9cb5-1d46385087e0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GainLossOnSaleOfPropertyPlantEquipment"/>
    <link:calculationArc order="10" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e280b-3653-73cc-b043-3cd6b73aa69a" xlink:to="loc_us-gaap_GainLossOnSaleOfPropertyPlantEquipment_019e280b-3653-71e5-9cb5-1d46385087e0" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccretionAmortizationOfDiscountsAndPremiumsInvestments_019e280b-3653-740f-9083-b3007c3205d9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccretionAmortizationOfDiscountsAndPremiumsInvestments"/>
    <link:calculationArc order="11" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e280b-3653-73cc-b043-3cd6b73aa69a" xlink:to="loc_us-gaap_AccretionAmortizationOfDiscountsAndPremiumsInvestments_019e280b-3653-740f-9083-b3007c3205d9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsly_AssetImpairmentChargesExcludingOperatingLeaseImpairment_019e280b-3653-7f6e-a4a0-7ed289b3a3a6" xlink:href="fsly-20260630.xsd#fsly_AssetImpairmentChargesExcludingOperatingLeaseImpairment"/>
    <link:calculationArc order="12" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e280b-3653-73cc-b043-3cd6b73aa69a" xlink:to="loc_fsly_AssetImpairmentChargesExcludingOperatingLeaseImpairment_019e280b-3653-7f6e-a4a0-7ed289b3a3a6" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaidInKindInterest_019e280b-3653-7b8c-a775-eb2725c08b93" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaidInKindInterest"/>
    <link:calculationArc order="13" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e280b-3653-73cc-b043-3cd6b73aa69a" xlink:to="loc_us-gaap_PaidInKindInterest_019e280b-3653-7b8c-a775-eb2725c08b93" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNoncashIncomeExpense_019e280b-3653-7af1-81e6-8f9f8d3c1420" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherNoncashIncomeExpense"/>
    <link:calculationArc order="14" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e280b-3653-73cc-b043-3cd6b73aa69a" xlink:to="loc_us-gaap_OtherNoncashIncomeExpense_019e280b-3653-7af1-81e6-8f9f8d3c1420" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_019e280b-3653-7bfc-8cf9-42261bbd0b7f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInAccountsReceivable"/>
    <link:calculationArc order="15" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e280b-3653-73cc-b043-3cd6b73aa69a" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_019e280b-3653-7bfc-8cf9-42261bbd0b7f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_019e280b-3653-78cb-99e2-f714829d962b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets"/>
    <link:calculationArc order="16" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e280b-3653-73cc-b043-3cd6b73aa69a" xlink:to="loc_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_019e280b-3653-78cb-99e2-f714829d962b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_019e280b-3653-7c7f-a629-3f9f7059cab4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInOtherOperatingAssets"/>
    <link:calculationArc order="17" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e280b-3653-73cc-b043-3cd6b73aa69a" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_019e280b-3653-7c7f-a629-3f9f7059cab4" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsPayable_019e280b-3653-72fb-b147-ac274788f4f0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInAccountsPayable"/>
    <link:calculationArc order="18" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e280b-3653-73cc-b043-3cd6b73aa69a" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsPayable_019e280b-3653-72fb-b147-ac274788f4f0" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccruedLiabilities_019e280b-3653-7772-9167-0c7df6df16fe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInAccruedLiabilities"/>
    <link:calculationArc order="19" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e280b-3653-73cc-b043-3cd6b73aa69a" xlink:to="loc_us-gaap_IncreaseDecreaseInAccruedLiabilities_019e280b-3653-7772-9167-0c7df6df16fe" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsly_IncreaseDecreaseInOperatingLeaseLiabilities_019e8685-f68e-72ca-97a3-89b23bf948df" xlink:href="fsly-20260630.xsd#fsly_IncreaseDecreaseInOperatingLeaseLiabilities"/>
    <link:calculationArc order="20" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e280b-3653-73cc-b043-3cd6b73aa69a" xlink:to="loc_fsly_IncreaseDecreaseInOperatingLeaseLiabilities_019e8685-f68e-72ca-97a3-89b23bf948df" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_019f2681-331b-7b57-90e0-160822810af8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInOtherOperatingLiabilities"/>
    <link:calculationArc order="21" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e280b-3653-73cc-b043-3cd6b73aa69a" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_019f2681-331b-7b57-90e0-160822810af8" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://fastly.com/role/InvestmentsandFairValueMeasurementsDetails" xlink:type="simple" xlink:href="fsly-20260630.xsd#InvestmentsandFairValueMeasurementsDetails"/>
  <link:calculationLink xlink:role="http://fastly.com/role/InvestmentsandFairValueMeasurementsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019e280b-3653-7433-9b3e-ea93ae9b7943" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_019e280b-3653-7ac1-820b-e24b1023d368" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019e280b-3653-7433-9b3e-ea93ae9b7943" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_019e280b-3653-7ac1-820b-e24b1023d368" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsly_CashAndCashEquivalentAndDebtSecuritiesAvailableForSaleFairValue_019e280b-3653-7de5-bf55-ca749cbe6515" xlink:href="fsly-20260630.xsd#fsly_CashAndCashEquivalentAndDebtSecuritiesAvailableForSaleFairValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_019e280b-3653-726b-b1c1-eeb38a0ce3fd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_fsly_CashAndCashEquivalentAndDebtSecuritiesAvailableForSaleFairValue_019e280b-3653-7de5-bf55-ca749cbe6515" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_019e280b-3653-726b-b1c1-eeb38a0ce3fd" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_019e280b-3653-7676-82bd-6b2862dbaa11" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_fsly_CashAndCashEquivalentAndDebtSecuritiesAvailableForSaleFairValue_019e280b-3653-7de5-bf55-ca749cbe6515" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_019e280b-3653-7676-82bd-6b2862dbaa11" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsly_CashAndCashEquivalentAndDebtSecuritiesAvailableForSaleAmortizedCost_019e280b-3653-76e9-84aa-6448846f7d4e" xlink:href="fsly-20260630.xsd#fsly_CashAndCashEquivalentAndDebtSecuritiesAvailableForSaleAmortizedCost"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019e280b-3653-7166-b184-d82d6e894fcd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_fsly_CashAndCashEquivalentAndDebtSecuritiesAvailableForSaleAmortizedCost_019e280b-3653-76e9-84aa-6448846f7d4e" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019e280b-3653-7166-b184-d82d6e894fcd" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_019e280b-3653-7242-a51b-fa9c277b6939" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_fsly_CashAndCashEquivalentAndDebtSecuritiesAvailableForSaleAmortizedCost_019e280b-3653-76e9-84aa-6448846f7d4e" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_019e280b-3653-7242-a51b-fa9c277b6939" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_019e280b-3653-73f4-afbb-20184bbe1fca" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_019e280b-3653-7de7-b830-62c7c979705a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_019e280b-3653-73f4-afbb-20184bbe1fca" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_019e280b-3653-7de7-b830-62c7c979705a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_019e280b-3653-7c01-8847-0c6c9e1457b6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_019e280b-3653-73f4-afbb-20184bbe1fca" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_019e280b-3653-7c01-8847-0c6c9e1457b6" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_019e280b-3653-76a5-87b9-bf47008853ac" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_019e280b-3653-73f4-afbb-20184bbe1fca" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_019e280b-3653-76a5-87b9-bf47008853ac" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://fastly.com/role/InvestmentsandFairValueMeasurementsDetails_1" xlink:type="simple" xlink:href="fsly-20260630.xsd#InvestmentsandFairValueMeasurementsDetails_1"/>
  <link:calculationLink xlink:role="http://fastly.com/role/InvestmentsandFairValueMeasurementsDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_fsly_CashAndCashEquivalentAndDebtSecuritiesAvailableForSaleAmortizedCost_019e280b-3653-7d8d-a583-7decff42572e" xlink:href="fsly-20260630.xsd#fsly_CashAndCashEquivalentAndDebtSecuritiesAvailableForSaleAmortizedCost"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_019e280b-3653-762e-9854-2fa5256284ab" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_fsly_CashAndCashEquivalentAndDebtSecuritiesAvailableForSaleAmortizedCost_019e280b-3653-7d8d-a583-7decff42572e" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_019e280b-3653-762e-9854-2fa5256284ab" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_019e280b-3653-7165-bade-9cc2f2b7ad3c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_fsly_CashAndCashEquivalentAndDebtSecuritiesAvailableForSaleAmortizedCost_019e280b-3653-7d8d-a583-7decff42572e" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_019e280b-3653-7165-bade-9cc2f2b7ad3c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsly_CashAndCashEquivalentAndDebtSecuritiesAvailableForSaleFairValue_019e280b-3653-78d9-b0ba-3e6cf6e325f5" xlink:href="fsly-20260630.xsd#fsly_CashAndCashEquivalentAndDebtSecuritiesAvailableForSaleFairValue"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_fsly_CashAndCashEquivalentAndDebtSecuritiesAvailableForSaleAmortizedCost_019e280b-3653-7d8d-a583-7decff42572e" xlink:to="loc_fsly_CashAndCashEquivalentAndDebtSecuritiesAvailableForSaleFairValue_019e280b-3653-78d9-b0ba-3e6cf6e325f5" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://fastly.com/role/BalanceSheetInformationScheduleofPropertyandEquipmentNetDetails" xlink:type="simple" xlink:href="fsly-20260630.xsd#BalanceSheetInformationScheduleofPropertyandEquipmentNetDetails"/>
  <link:calculationLink xlink:role="http://fastly.com/role/BalanceSheetInformationScheduleofPropertyandEquipmentNetDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization_019e280b-3653-7e29-92a7-116212d7fe7b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization_019e280b-3653-7ab5-a77a-1364c177b345" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization_019e280b-3653-7e29-92a7-116212d7fe7b" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization_019e280b-3653-7ab5-a77a-1364c177b345" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAccumulatedDepreciationAndAmortization_019e280b-3653-7eeb-ace1-56963e1dd29a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAccumulatedDepreciationAndAmortization"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization_019e280b-3653-7e29-92a7-116212d7fe7b" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAccumulatedDepreciationAndAmortization_019e280b-3653-7eeb-ace1-56963e1dd29a" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://fastly.com/role/BalanceSheetInformationScheduleofOtherAssetsDetails" xlink:type="simple" xlink:href="fsly-20260630.xsd#BalanceSheetInformationScheduleofOtherAssetsDetails"/>
  <link:calculationLink xlink:role="http://fastly.com/role/BalanceSheetInformationScheduleofOtherAssetsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_019e280b-3653-700b-8196-80302965abee" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherAssetsNoncurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsMiscellaneousNoncurrent_019e280b-3653-7f2f-8672-e9c6e7de7879" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherAssetsMiscellaneousNoncurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OtherAssetsNoncurrent_019e280b-3653-700b-8196-80302965abee" xlink:to="loc_us-gaap_OtherAssetsMiscellaneousNoncurrent_019e280b-3653-7f2f-8672-e9c6e7de7879" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostNetNoncurrent_019e280b-3653-7e12-a45f-d8abe351d8e9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CapitalizedContractCostNetNoncurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OtherAssetsNoncurrent_019e280b-3653-700b-8196-80302965abee" xlink:to="loc_us-gaap_CapitalizedContractCostNetNoncurrent_019e280b-3653-7e12-a45f-d8abe351d8e9" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://fastly.com/role/BalanceSheetInformationScheduleofAccruedExpensesDetails" xlink:type="simple" xlink:href="fsly-20260630.xsd#BalanceSheetInformationScheduleofAccruedExpensesDetails"/>
  <link:calculationLink xlink:role="http://fastly.com/role/BalanceSheetInformationScheduleofAccruedExpensesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedLiabilitiesCurrent_019e280b-3653-7970-8815-fcae23881039" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccruedLiabilitiesCurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccrualForTaxesOtherThanIncomeTaxesCurrent_019e280b-3653-7160-bdef-5c3354ed5e0c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccrualForTaxesOtherThanIncomeTaxesCurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AccruedLiabilitiesCurrent_019e280b-3653-7970-8815-fcae23881039" xlink:to="loc_us-gaap_AccrualForTaxesOtherThanIncomeTaxesCurrent_019e280b-3653-7160-bdef-5c3354ed5e0c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeRelatedLiabilitiesCurrent_019e280b-3653-7dd9-9274-2b03df26cab8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeRelatedLiabilitiesCurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AccruedLiabilitiesCurrent_019e280b-3653-7970-8815-fcae23881039" xlink:to="loc_us-gaap_EmployeeRelatedLiabilitiesCurrent_019e280b-3653-7dd9-9274-2b03df26cab8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsly_AccruedColocationAndBandwidthCosts_019e280b-3653-7bcc-bbca-aa681a26a31c" xlink:href="fsly-20260630.xsd#fsly_AccruedColocationAndBandwidthCosts"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AccruedLiabilitiesCurrent_019e280b-3653-7970-8815-fcae23881039" xlink:to="loc_fsly_AccruedColocationAndBandwidthCosts_019e280b-3653-7bcc-bbca-aa681a26a31c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAccruedLiabilitiesCurrent_019e280b-3653-77fd-b8a4-f5c6b669d54d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherAccruedLiabilitiesCurrent"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AccruedLiabilitiesCurrent_019e280b-3653-7970-8815-fcae23881039" xlink:to="loc_us-gaap_OtherAccruedLiabilitiesCurrent_019e280b-3653-77fd-b8a4-f5c6b669d54d" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://fastly.com/role/LeasesScheduleofComponentsofOperatingLeaseCostDetails" xlink:type="simple" xlink:href="fsly-20260630.xsd#LeasesScheduleofComponentsofOperatingLeaseCostDetails"/>
  <link:calculationLink xlink:role="http://fastly.com/role/LeasesScheduleofComponentsofOperatingLeaseCostDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_fsly_OperatingVariableAndShortTermLeaseCosts_019e280b-3653-7326-b4bf-a3d1df8965b0" xlink:href="fsly-20260630.xsd#fsly_OperatingVariableAndShortTermLeaseCosts"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseCost_019e280b-3653-7cc6-87ec-c59f49169dc6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseCost"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_fsly_OperatingVariableAndShortTermLeaseCosts_019e280b-3653-7326-b4bf-a3d1df8965b0" xlink:to="loc_us-gaap_OperatingLeaseCost_019e280b-3653-7cc6-87ec-c59f49169dc6" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableLeaseCost_019e280b-3653-7686-8cae-36d34786d66f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VariableLeaseCost"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_fsly_OperatingVariableAndShortTermLeaseCosts_019e280b-3653-7326-b4bf-a3d1df8965b0" xlink:to="loc_us-gaap_VariableLeaseCost_019e280b-3653-7686-8cae-36d34786d66f" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://fastly.com/role/LeasesScheduleofFutureMinimumLeasePaymentsUnderNonCancellableLeasesDetails" xlink:type="simple" xlink:href="fsly-20260630.xsd#LeasesScheduleofFutureMinimumLeasePaymentsUnderNonCancellableLeasesDetails"/>
  <link:calculationLink xlink:role="http://fastly.com/role/LeasesScheduleofFutureMinimumLeasePaymentsUnderNonCancellableLeasesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019e280b-3653-735a-b37a-a373fa0a8263" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_019e280b-3653-708d-97d4-ff08ea0cc874" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019e280b-3653-735a-b37a-a373fa0a8263" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_019e280b-3653-708d-97d4-ff08ea0cc874" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiability_019e280b-3653-7d43-a934-7de24a0c3303" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseLiability"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019e280b-3653-735a-b37a-a373fa0a8263" xlink:to="loc_us-gaap_OperatingLeaseLiability_019e280b-3653-7d43-a934-7de24a0c3303" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://fastly.com/role/LeasesScheduleofFutureMinimumLeasePaymentsUnderNonCancellableLeasesDetails_1" xlink:type="simple" xlink:href="fsly-20260630.xsd#LeasesScheduleofFutureMinimumLeasePaymentsUnderNonCancellableLeasesDetails_1"/>
  <link:calculationLink xlink:role="http://fastly.com/role/LeasesScheduleofFutureMinimumLeasePaymentsUnderNonCancellableLeasesDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019e280b-3653-738b-81cf-caac147fac58" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear_019e280b-3653-780d-8236-b06c6e46acd6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019e280b-3653-738b-81cf-caac147fac58" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear_019e280b-3653-780d-8236-b06c6e46acd6" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_019e280b-3653-7286-bb6d-3877014f642c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019e280b-3653-738b-81cf-caac147fac58" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_019e280b-3653-7286-bb6d-3877014f642c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_019e280b-3653-7f66-8541-0e48383ef344" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019e280b-3653-738b-81cf-caac147fac58" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_019e280b-3653-7f66-8541-0e48383ef344" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_019e280b-3653-7a32-9a92-a84e4177760b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019e280b-3653-738b-81cf-caac147fac58" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_019e280b-3653-7a32-9a92-a84e4177760b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_019e280b-3653-75fa-9cf2-c55ecb5ce6dc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019e280b-3653-738b-81cf-caac147fac58" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_019e280b-3653-75fa-9cf2-c55ecb5ce6dc" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsly_LesseeOperatingLeaseLiabilityToBePaidAfterYearFour_019e280b-3653-7c63-a176-a5c203cf2a68" xlink:href="fsly-20260630.xsd#fsly_LesseeOperatingLeaseLiabilityToBePaidAfterYearFour"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019e280b-3653-738b-81cf-caac147fac58" xlink:to="loc_fsly_LesseeOperatingLeaseLiabilityToBePaidAfterYearFour_019e280b-3653-7c63-a176-a5c203cf2a68" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://fastly.com/role/GoodwillandIntangibleAssetsScheduleofIntangibleAssetsDetails" xlink:type="simple" xlink:href="fsly-20260630.xsd#GoodwillandIntangibleAssetsScheduleofIntangibleAssetsDetails"/>
  <link:calculationLink xlink:role="http://fastly.com/role/GoodwillandIntangibleAssetsScheduleofIntangibleAssetsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_019e280b-3654-75b3-bd16-020e9b29e00e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_019e280b-3654-7671-83f5-69a3f83cfea7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNet_019e280b-3654-75b3-bd16-020e9b29e00e" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_019e280b-3654-7671-83f5-69a3f83cfea7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_019e280b-3654-711c-8b1b-144fafb64858" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNet_019e280b-3654-75b3-bd16-020e9b29e00e" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_019e280b-3654-711c-8b1b-144fafb64858" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://fastly.com/role/GoodwillandIntangibleAssetsScheduleofExpectedAmortizationExpenseofIntangibleAssetsDetails" xlink:type="simple" xlink:href="fsly-20260630.xsd#GoodwillandIntangibleAssetsScheduleofExpectedAmortizationExpenseofIntangibleAssetsDetails"/>
  <link:calculationLink xlink:role="http://fastly.com/role/GoodwillandIntangibleAssetsScheduleofExpectedAmortizationExpenseofIntangibleAssetsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_019e280b-3654-77d7-9b8a-4b4e73f6ac3f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseRemainderOfFiscalYear_019e280b-3654-7206-bac5-9913c4069c53" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseRemainderOfFiscalYear"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNet_019e280b-3654-77d7-9b8a-4b4e73f6ac3f" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseRemainderOfFiscalYear_019e280b-3654-7206-bac5-9913c4069c53" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths_019e280b-3654-7e04-ba62-fb705f5fc4f8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNet_019e280b-3654-77d7-9b8a-4b4e73f6ac3f" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths_019e280b-3654-7e04-ba62-fb705f5fc4f8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo_019e280b-3654-7e0e-b7d6-dbff7faa0cdc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNet_019e280b-3654-77d7-9b8a-4b4e73f6ac3f" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo_019e280b-3654-7e0e-b7d6-dbff7faa0cdc" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree_019e280b-3654-7aed-b649-b4e662f88642" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNet_019e280b-3654-77d7-9b8a-4b4e73f6ac3f" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree_019e280b-3654-7aed-b649-b4e662f88642" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour_019e280b-3654-793b-a703-1d4daf817573" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNet_019e280b-3654-77d7-9b8a-4b4e73f6ac3f" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour_019e280b-3654-793b-a703-1d4daf817573" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsly_IntangibleAssetFiniteLivedEstimatedAmortizationExpenseAfterYearFour_019e280b-3654-7ead-8269-5228b960ca64" xlink:href="fsly-20260630.xsd#fsly_IntangibleAssetFiniteLivedEstimatedAmortizationExpenseAfterYearFour"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNet_019e280b-3654-77d7-9b8a-4b4e73f6ac3f" xlink:to="loc_fsly_IntangibleAssetFiniteLivedEstimatedAmortizationExpenseAfterYearFour_019e280b-3654-7ead-8269-5228b960ca64" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://fastly.com/role/DebtInstrumentsScheduleofCarryingValueofNotesDetails" xlink:type="simple" xlink:href="fsly-20260630.xsd#DebtInstrumentsScheduleofCarryingValueofNotesDetails"/>
  <link:calculationLink xlink:role="http://fastly.com/role/DebtInstrumentsScheduleofCarryingValueofNotesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_019e280b-3654-7643-89ac-4c97fc62440b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebt"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_019e280b-3654-7928-b5bd-d0676bfc0ba4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LongTermDebt_019e280b-3654-7643-89ac-4c97fc62440b" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_019e280b-3654-7928-b5bd-d0676bfc0ba4" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_019e280b-3654-7bcc-81c3-3a4aecb31c89" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LongTermDebt_019e280b-3654-7643-89ac-4c97fc62440b" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_019e280b-3654-7bcc-81c3-3a4aecb31c89" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://fastly.com/role/CommitmentsandContingenciesDetails" xlink:type="simple" xlink:href="fsly-20260630.xsd#CommitmentsandContingenciesDetails"/>
  <link:calculationLink xlink:role="http://fastly.com/role/CommitmentsandContingenciesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PurchaseObligation_019e280b-3654-72ea-ab63-cc4459384a0f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PurchaseObligation"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsly_PurchaseObligationToBePaidAfterYearFour_019e280b-3654-7157-94d9-c59dc53f93b1" xlink:href="fsly-20260630.xsd#fsly_PurchaseObligationToBePaidAfterYearFour"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_PurchaseObligation_019e280b-3654-72ea-ab63-cc4459384a0f" xlink:to="loc_fsly_PurchaseObligationToBePaidAfterYearFour_019e280b-3654-7157-94d9-c59dc53f93b1" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PurchaseObligationDueInFourthYear_019e280b-3654-7da5-9398-8e0118e336b7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PurchaseObligationDueInFourthYear"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_PurchaseObligation_019e280b-3654-72ea-ab63-cc4459384a0f" xlink:to="loc_us-gaap_PurchaseObligationDueInFourthYear_019e280b-3654-7da5-9398-8e0118e336b7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PurchaseObligationFutureMinimumPaymentsRemainderOfFiscalYear_019e280b-3654-78ee-8ab6-1568a57d7f59" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PurchaseObligationFutureMinimumPaymentsRemainderOfFiscalYear"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_PurchaseObligation_019e280b-3654-72ea-ab63-cc4459384a0f" xlink:to="loc_us-gaap_PurchaseObligationFutureMinimumPaymentsRemainderOfFiscalYear_019e280b-3654-78ee-8ab6-1568a57d7f59" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PurchaseObligationDueInThirdYear_019e280b-3654-711b-848e-8361ddbde2e2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PurchaseObligationDueInThirdYear"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_PurchaseObligation_019e280b-3654-72ea-ab63-cc4459384a0f" xlink:to="loc_us-gaap_PurchaseObligationDueInThirdYear_019e280b-3654-711b-848e-8361ddbde2e2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PurchaseObligationDueInSecondYear_019e280b-3654-7cf5-a603-9047ddc1ae9a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PurchaseObligationDueInSecondYear"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_PurchaseObligation_019e280b-3654-72ea-ab63-cc4459384a0f" xlink:to="loc_us-gaap_PurchaseObligationDueInSecondYear_019e280b-3654-7cf5-a603-9047ddc1ae9a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PurchaseObligationDueInNextTwelveMonths_019e280b-3654-726c-9aac-47cc15b1a2c1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PurchaseObligationDueInNextTwelveMonths"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_PurchaseObligation_019e280b-3654-72ea-ab63-cc4459384a0f" xlink:to="loc_us-gaap_PurchaseObligationDueInNextTwelveMonths_019e280b-3654-726c-9aac-47cc15b1a2c1" xlink:type="arc"/>
  </link:calculationLink>
</link:linkbase>
