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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019ef5bf-f8f4-7013-aa54-d88a84576ae1,g:ec1b69b0-0062-426f-96de-02ffee37b94f-->
<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:roleRef roleURI="http://golubcapitalbdc.com/role/ConsolidatedStatementsofFinancialCondition" xlink:type="simple" xlink:href="gbdc4-20250930.xsd#ConsolidatedStatementsofFinancialCondition"/>
  <link:calculationLink xlink:role="http://golubcapitalbdc.com/role/ConsolidatedStatementsofFinancialCondition" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_019ef5c0-0bf9-73b4-ba5c-50fd1f6e4e25" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingencies_019ef5c0-0bf9-73e6-b696-352c5e9409de" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommitmentsAndContingencies"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquity_019ef5c0-0bf9-73b4-ba5c-50fd1f6e4e25" xlink:to="loc_us-gaap_CommitmentsAndContingencies_019ef5c0-0bf9-73e6-b696-352c5e9409de" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_019ef5c0-0bf9-76dd-b167-5abd4c613fe9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Liabilities"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquity_019ef5c0-0bf9-73b4-ba5c-50fd1f6e4e25" xlink:to="loc_us-gaap_Liabilities_019ef5c0-0bf9-76dd-b167-5abd4c613fe9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019ef5c0-0bf9-78e7-8b8a-6d91a0554b6a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquity_019ef5c0-0bf9-73b4-ba5c-50fd1f6e4e25" xlink:to="loc_us-gaap_StockholdersEquity_019ef5c0-0bf9-78e7-8b8a-6d91a0554b6a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_019ef5c0-0bf9-7b6f-9622-ecfeacd47ae6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Liabilities"/>
    <link:loc xlink:type="locator" xlink:label="loc_gbdc4_AccruedTrusteeFees_019ef5c0-0bf9-7607-8803-5d10ef923fc7" xlink:href="gbdc4-20250930.xsd#gbdc4_AccruedTrusteeFees"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019ef5c0-0bf9-7b6f-9622-ecfeacd47ae6" xlink:to="loc_gbdc4_AccruedTrusteeFees_019ef5c0-0bf9-7607-8803-5d10ef923fc7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableAndOtherAccruedLiabilities_019ef5c0-0bf9-7434-ad29-3c067ca51a3c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsPayableAndOtherAccruedLiabilities"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019ef5c0-0bf9-7b6f-9622-ecfeacd47ae6" xlink:to="loc_us-gaap_AccountsPayableAndOtherAccruedLiabilities_019ef5c0-0bf9-7434-ad29-3c067ca51a3c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_019ef5c0-0bf9-791a-8e99-9e0f6c8deb36" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebt"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019ef5c0-0bf9-7b6f-9622-ecfeacd47ae6" xlink:to="loc_us-gaap_LongTermDebt_019ef5c0-0bf9-791a-8e99-9e0f6c8deb36" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestPayableCurrentAndNoncurrent_019ef5c0-0bf9-7d4b-8aae-24a05d134e02" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestPayableCurrentAndNoncurrent"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019ef5c0-0bf9-7b6f-9622-ecfeacd47ae6" xlink:to="loc_us-gaap_InterestPayableCurrentAndNoncurrent_019ef5c0-0bf9-7d4b-8aae-24a05d134e02" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DistributionPayable_019ef5c0-0bf9-7d1e-a8b5-6be9f50d5fc8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DistributionPayable"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019ef5c0-0bf9-7b6f-9622-ecfeacd47ae6" xlink:to="loc_us-gaap_DistributionPayable_019ef5c0-0bf9-7d1e-a8b5-6be9f50d5fc8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ManagementAndIncentiveFeesPayable_019ef5c0-0bf9-7b70-aa8d-47fa869aface" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ManagementAndIncentiveFeesPayable"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019ef5c0-0bf9-7b6f-9622-ecfeacd47ae6" xlink:to="loc_us-gaap_ManagementAndIncentiveFeesPayable_019ef5c0-0bf9-7b70-aa8d-47fa869aface" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilities_019ef5c0-0bf9-7ce8-810a-251b3d8e6fa6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLiabilities"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019ef5c0-0bf9-7b6f-9622-ecfeacd47ae6" xlink:to="loc_us-gaap_DerivativeLiabilities_019ef5c0-0bf9-7ce8-810a-251b3d8e6fa6" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_019ef5c0-0bf9-7183-adee-40df3d4a3e4a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Assets"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentOwnedAtFairValue_019ef5c0-0bf9-7d5a-a854-ab3434aea186" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentOwnedAtFairValue"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019ef5c0-0bf9-7183-adee-40df3d4a3e4a" xlink:to="loc_us-gaap_InvestmentOwnedAtFairValue_019ef5c0-0bf9-7d5a-a854-ab3434aea186" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019ef5c0-0bf9-7e27-8c3c-515f04c66583" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019ef5c0-0bf9-7183-adee-40df3d4a3e4a" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019ef5c0-0bf9-7e27-8c3c-515f04c66583" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashHeldInForeignCurrency_019ef5c0-0bf9-7e7e-b5bb-2cf234acaac0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashHeldInForeignCurrency"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019ef5c0-0bf9-7183-adee-40df3d4a3e4a" xlink:to="loc_us-gaap_CashHeldInForeignCurrency_019ef5c0-0bf9-7e7e-b5bb-2cf234acaac0" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalents_019ef5c0-0bf9-7c25-8600-96b83f2ed051" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestrictedCashAndCashEquivalents"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019ef5c0-0bf9-7183-adee-40df3d4a3e4a" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalents_019ef5c0-0bf9-7c25-8600-96b83f2ed051" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gbdc4_RestrictedCashHeldInForeignCurrency_019ef5c0-0bf9-7155-9383-d3629a7af8b2" xlink:href="gbdc4-20250930.xsd#gbdc4_RestrictedCashHeldInForeignCurrency"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019ef5c0-0bf9-7183-adee-40df3d4a3e4a" xlink:to="loc_gbdc4_RestrictedCashHeldInForeignCurrency_019ef5c0-0bf9-7155-9383-d3629a7af8b2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestReceivable_019ef5c0-0bf9-79f2-b2a4-0835ba3a9071" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestReceivable"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019ef5c0-0bf9-7183-adee-40df3d4a3e4a" xlink:to="loc_us-gaap_InterestReceivable_019ef5c0-0bf9-79f2-b2a4-0835ba3a9071" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReceivableInvestmentSale_019ef5c0-0bf9-70c1-b691-95ba339fbd1c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ReceivableInvestmentSale"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019ef5c0-0bf9-7183-adee-40df3d4a3e4a" xlink:to="loc_us-gaap_ReceivableInvestmentSale_019ef5c0-0bf9-70c1-b691-95ba339fbd1c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gbdc4_CapitalCallReceivable_019ef5c0-0bf9-7fef-b1b1-1bbb9a51a416" xlink:href="gbdc4-20250930.xsd#gbdc4_CapitalCallReceivable"/>
    <link:calculationArc order="8" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019ef5c0-0bf9-7183-adee-40df3d4a3e4a" xlink:to="loc_gbdc4_CapitalCallReceivable_019ef5c0-0bf9-7fef-b1b1-1bbb9a51a416" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredOfferingCosts_019ef5c0-0bf9-73b9-9364-31f928ba3411" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredOfferingCosts"/>
    <link:calculationArc order="9" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019ef5c0-0bf9-7183-adee-40df3d4a3e4a" xlink:to="loc_us-gaap_DeferredOfferingCosts_019ef5c0-0bf9-73b9-9364-31f928ba3411" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssets_019ef5c0-0bf9-7338-9a30-e7051f48cc7d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherAssets"/>
    <link:calculationArc order="10" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019ef5c0-0bf9-7183-adee-40df3d4a3e4a" xlink:to="loc_us-gaap_OtherAssets_019ef5c0-0bf9-7338-9a30-e7051f48cc7d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_019ef5c0-0bf9-7268-bcbf-164e2d2ab40a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebt"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_019ef5c0-0bf9-768d-954e-22496c5f4047" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LongTermDebt_019ef5c0-0bf9-7268-bcbf-164e2d2ab40a" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_019ef5c0-0bf9-768d-954e-22496c5f4047" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_019ef5c0-0bf9-781a-a2aa-69dd351124d7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LongTermDebt_019ef5c0-0bf9-7268-bcbf-164e2d2ab40a" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_019ef5c0-0bf9-781a-a2aa-69dd351124d7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019ef5c0-0bf9-7967-aacd-b2f7800b75b7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapital_019ef5c0-0bf9-7e27-8ebf-c603da49fa23" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdditionalPaidInCapital"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_019ef5c0-0bf9-7967-aacd-b2f7800b75b7" xlink:to="loc_us-gaap_AdditionalPaidInCapital_019ef5c0-0bf9-7e27-8ebf-c603da49fa23" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockValue_019ef5c0-0bf9-7b65-bf70-b8fda8b08050" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockValue"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_019ef5c0-0bf9-7967-aacd-b2f7800b75b7" xlink:to="loc_us-gaap_PreferredStockValue_019ef5c0-0bf9-7b65-bf70-b8fda8b08050" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValue_019ef5c0-0bf9-706b-a0a2-b99d90edcff0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockValue"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_019ef5c0-0bf9-7967-aacd-b2f7800b75b7" xlink:to="loc_us-gaap_CommonStockValue_019ef5c0-0bf9-706b-a0a2-b99d90edcff0" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_019ef5c0-0bf9-7e0b-a8bb-1f8f90caa56f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_019ef5c0-0bf9-7967-aacd-b2f7800b75b7" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_019ef5c0-0bf9-7e0b-a8bb-1f8f90caa56f" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://golubcapitalbdc.com/role/ConsolidatedStatementsofOperations" xlink:type="simple" xlink:href="gbdc4-20250930.xsd#ConsolidatedStatementsofOperations"/>
  <link:calculationLink xlink:role="http://golubcapitalbdc.com/role/ConsolidatedStatementsofOperations" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetInvestmentIncome_019ef5c0-0bf9-7446-9da0-7fe184e3f869" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetInvestmentIncome"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyExpenseAfterReductionOfFeeWaiverAndReimbursement_019ef5c0-0bf9-7188-8cd6-f2734ee896d7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyExpenseAfterReductionOfFeeWaiverAndReimbursement"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetInvestmentIncome_019ef5c0-0bf9-7446-9da0-7fe184e3f869" xlink:to="loc_us-gaap_InvestmentCompanyExpenseAfterReductionOfFeeWaiverAndReimbursement_019ef5c0-0bf9-7188-8cd6-f2734ee896d7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrossInvestmentIncomeOperating_019ef5c0-0bf9-714c-befd-777baf17c459" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GrossInvestmentIncomeOperating"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetInvestmentIncome_019ef5c0-0bf9-7446-9da0-7fe184e3f869" xlink:to="loc_us-gaap_GrossInvestmentIncomeOperating_019ef5c0-0bf9-714c-befd-777baf17c459" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealizedAndUnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingBeforeTax_019ef5c0-0bf9-7765-a40a-4958afed70cf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RealizedAndUnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingBeforeTax"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingBeforeTax_019ef5c0-0bf9-7cb1-97b0-3ddc97e455c8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingBeforeTax"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_RealizedAndUnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingBeforeTax_019ef5c0-0bf9-7765-a40a-4958afed70cf" xlink:to="loc_us-gaap_RealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingBeforeTax_019ef5c0-0bf9-7cb1-97b0-3ddc97e455c8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingBeforeTax_019ef5c0-0bf9-70e1-bca5-16c58a65c8a6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingBeforeTax"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_RealizedAndUnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingBeforeTax_019ef5c0-0bf9-7765-a40a-4958afed70cf" xlink:to="loc_us-gaap_UnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingBeforeTax_019ef5c0-0bf9-70e1-bca5-16c58a65c8a6" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingBeforeTax_019ef5c0-0bf9-7872-a5ea-bd02893f9a34" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingBeforeTax"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtAndEquitySecuritiesRealizedGainLoss_019ef5c0-0bf9-70ed-b1fd-84682944b6d3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtAndEquitySecuritiesRealizedGainLoss"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_RealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingBeforeTax_019ef5c0-0bf9-7872-a5ea-bd02893f9a34" xlink:to="loc_us-gaap_DebtAndEquitySecuritiesRealizedGainLoss_019ef5c0-0bf9-70ed-b1fd-84682944b6d3" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyTransactionGainLossRealized_019ef5c0-0bf9-7f64-8c3d-54d3c594936b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignCurrencyTransactionGainLossRealized"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_RealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingBeforeTax_019ef5c0-0bf9-7872-a5ea-bd02893f9a34" xlink:to="loc_us-gaap_ForeignCurrencyTransactionGainLossRealized_019ef5c0-0bf9-7f64-8c3d-54d3c594936b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIncomeOperatingAfterExpenseAndTax_019ef5c0-0bf9-7c90-ae2f-6bfce5c3e6ed" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentIncomeOperatingAfterExpenseAndTax"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIncomeOperatingTaxExpenseBenefit_019ef5c0-0bf9-7701-bb5e-c1eda0529fb1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentIncomeOperatingTaxExpenseBenefit"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentIncomeOperatingAfterExpenseAndTax_019ef5c0-0bf9-7c90-ae2f-6bfce5c3e6ed" xlink:to="loc_us-gaap_InvestmentIncomeOperatingTaxExpenseBenefit_019ef5c0-0bf9-7701-bb5e-c1eda0529fb1" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetInvestmentIncome_019ef5c0-0bf9-76f3-842a-2fe29e0b3c87" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetInvestmentIncome"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentIncomeOperatingAfterExpenseAndTax_019ef5c0-0bf9-7c90-ae2f-6bfce5c3e6ed" xlink:to="loc_us-gaap_NetInvestmentIncome_019ef5c0-0bf9-76f3-842a-2fe29e0b3c87" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingBeforeTax_019ef5c0-0bf9-79f3-9da4-17e3ae273fd1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingBeforeTax"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyTransactionGainLossUnrealized_019ef5c0-0bf9-75f6-a8e9-1c31b4d7cad2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignCurrencyTransactionGainLossUnrealized"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_UnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingBeforeTax_019ef5c0-0bf9-79f3-9da4-17e3ae273fd1" xlink:to="loc_us-gaap_ForeignCurrencyTransactionGainLossUnrealized_019ef5c0-0bf9-75f6-a8e9-1c31b4d7cad2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrealizedGainLossOnDerivatives_019ef5c0-0bf9-7f3a-a77c-f5e8a483f965" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnrealizedGainLossOnDerivatives"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_UnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingBeforeTax_019ef5c0-0bf9-79f3-9da4-17e3ae273fd1" xlink:to="loc_us-gaap_UnrealizedGainLossOnDerivatives_019ef5c0-0bf9-7f3a-a77c-f5e8a483f965" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss_019ef5c0-0bf9-7160-8e29-7ea58093d32c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_UnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingBeforeTax_019ef5c0-0bf9-79f3-9da4-17e3ae273fd1" xlink:to="loc_us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss_019ef5c0-0bf9-7160-8e29-7ea58093d32c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyExpenseAfterReductionOfFeeWaiverAndReimbursement_019ef5c0-0bf9-76d9-931a-60a38316a580" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyExpenseAfterReductionOfFeeWaiverAndReimbursement"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIncomeInvestmentExpense_019ef5c0-0bf9-7b93-99ce-f1727278b824" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentIncomeInvestmentExpense"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentCompanyExpenseAfterReductionOfFeeWaiverAndReimbursement_019ef5c0-0bf9-76d9-931a-60a38316a580" xlink:to="loc_us-gaap_InvestmentIncomeInvestmentExpense_019ef5c0-0bf9-7b93-99ce-f1727278b824" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyManagementFeeContractualFeeWaived_019ef5c0-0bf9-7b8a-92e1-4792664cdf0a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyManagementFeeContractualFeeWaived"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentCompanyExpenseAfterReductionOfFeeWaiverAndReimbursement_019ef5c0-0bf9-76d9-931a-60a38316a580" xlink:to="loc_us-gaap_InvestmentCompanyManagementFeeContractualFeeWaived_019ef5c0-0bf9-7b8a-92e1-4792664cdf0a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyIncentiveFeeWaived_019ef5c0-0bf9-7865-8b93-31aeeae6b0b5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyIncentiveFeeWaived"/>
    <link:calculationArc order="3" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentCompanyExpenseAfterReductionOfFeeWaiverAndReimbursement_019ef5c0-0bf9-76d9-931a-60a38316a580" xlink:to="loc_us-gaap_InvestmentCompanyIncentiveFeeWaived_019ef5c0-0bf9-7865-8b93-31aeeae6b0b5" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019ef5c0-0bf9-7a18-adad-3646c4c13805" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIncomeOperatingAfterExpenseAndTax_019ef5c0-0bf9-7328-b987-4b68ade0cdda" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentIncomeOperatingAfterExpenseAndTax"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetIncomeLoss_019ef5c0-0bf9-7a18-adad-3646c4c13805" xlink:to="loc_us-gaap_InvestmentIncomeOperatingAfterExpenseAndTax_019ef5c0-0bf9-7328-b987-4b68ade0cdda" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealizedAndUnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingBeforeTax_019ef5c0-0bf9-77b4-b9e4-6d62ccb64d6d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RealizedAndUnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingBeforeTax"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetIncomeLoss_019ef5c0-0bf9-7a18-adad-3646c4c13805" xlink:to="loc_us-gaap_RealizedAndUnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingBeforeTax_019ef5c0-0bf9-77b4-b9e4-6d62ccb64d6d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrossInvestmentIncomeOperating_019ef5c0-0bf9-78e9-95d7-ffbdcf4a7ade" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GrossInvestmentIncomeOperating"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeOperatingPaidInCash_019ef5c0-0bf9-714b-948b-b0166c4679ba" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestIncomeOperatingPaidInCash"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_GrossInvestmentIncomeOperating_019ef5c0-0bf9-78e9-95d7-ffbdcf4a7ade" xlink:to="loc_us-gaap_InterestIncomeOperatingPaidInCash_019ef5c0-0bf9-714b-948b-b0166c4679ba" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendIncomeOperating_019ef5c0-0bf9-73e1-ab40-59c38b674e2a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DividendIncomeOperating"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_GrossInvestmentIncomeOperating_019ef5c0-0bf9-78e9-95d7-ffbdcf4a7ade" xlink:to="loc_us-gaap_DividendIncomeOperating_019ef5c0-0bf9-73e1-ab40-59c38b674e2a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeOperatingPaidInKind_019ef5c0-0bf9-7b14-bc50-eaf2852d1bf4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestIncomeOperatingPaidInKind"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_GrossInvestmentIncomeOperating_019ef5c0-0bf9-78e9-95d7-ffbdcf4a7ade" xlink:to="loc_us-gaap_InterestIncomeOperatingPaidInKind_019ef5c0-0bf9-7b14-bc50-eaf2852d1bf4" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FeeIncome_019ef5c0-0bf9-78ab-ab33-9f022b7a1cda" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FeeIncome"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_GrossInvestmentIncomeOperating_019ef5c0-0bf9-78e9-95d7-ffbdcf4a7ade" xlink:to="loc_us-gaap_FeeIncome_019ef5c0-0bf9-78ab-ab33-9f022b7a1cda" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIncomeInvestmentExpense_019ef5c0-0bf9-72b6-806a-995107669e5e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentIncomeInvestmentExpense"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdministrativeFeesExpense_019ef5c0-0bf9-74d4-ab74-f5c2cec9e83d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdministrativeFeesExpense"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentIncomeInvestmentExpense_019ef5c0-0bf9-72b6-806a-995107669e5e" xlink:to="loc_us-gaap_AdministrativeFeesExpense_019ef5c0-0bf9-74d4-ab74-f5c2cec9e83d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseOperating_019ef5c0-0bf9-79a0-9fd7-d4600f803722" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestExpenseOperating"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentIncomeInvestmentExpense_019ef5c0-0bf9-72b6-806a-995107669e5e" xlink:to="loc_us-gaap_InterestExpenseOperating_019ef5c0-0bf9-79a0-9fd7-d4600f803722" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncentiveFeeExpense_019ef5c0-0bf9-7fb0-a3a1-fcf196cfafb4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncentiveFeeExpense"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentIncomeInvestmentExpense_019ef5c0-0bf9-72b6-806a-995107669e5e" xlink:to="loc_us-gaap_IncentiveFeeExpense_019ef5c0-0bf9-7fb0-a3a1-fcf196cfafb4" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpense_019ef5c0-0bf9-71c8-bc05-3ec39edcab04" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GeneralAndAdministrativeExpense"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentIncomeInvestmentExpense_019ef5c0-0bf9-72b6-806a-995107669e5e" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpense_019ef5c0-0bf9-71c8-bc05-3ec39edcab04" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfessionalFees_019ef5c0-0bf9-74e0-a69f-b7afcaa0daac" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProfessionalFees"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentIncomeInvestmentExpense_019ef5c0-0bf9-72b6-806a-995107669e5e" xlink:to="loc_us-gaap_ProfessionalFees_019ef5c0-0bf9-74e0-a69f-b7afcaa0daac" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ManagementFeeExpense_019ef5c0-0bf9-7816-9cfa-8408f8d8be3a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ManagementFeeExpense"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentIncomeInvestmentExpense_019ef5c0-0bf9-72b6-806a-995107669e5e" xlink:to="loc_us-gaap_ManagementFeeExpense_019ef5c0-0bf9-7816-9cfa-8408f8d8be3a" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://golubcapitalbdc.com/role/ConsolidatedStatementsofChangesinNetAssets" xlink:type="simple" xlink:href="gbdc4-20250930.xsd#ConsolidatedStatementsofChangesinNetAssets"/>
  <link:calculationLink xlink:role="http://golubcapitalbdc.com/role/ConsolidatedStatementsofChangesinNetAssets" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesPeriodIncreaseDecrease_019ef5c0-0bf9-75ff-bfdd-02a5740338eb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodSharesPeriodIncreaseDecrease"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan_019ef5c0-0bf9-7bcd-8f9e-d4ea709ed4a8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockIssuedDuringPeriodSharesPeriodIncreaseDecrease_019ef5c0-0bf9-75ff-bfdd-02a5740338eb" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan_019ef5c0-0bf9-7bcd-8f9e-d4ea709ed4a8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_019ef5c0-0bf9-7777-adac-5fb26ab7efb0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockIssuedDuringPeriodSharesPeriodIncreaseDecrease_019ef5c0-0bf9-75ff-bfdd-02a5740338eb" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_019ef5c0-0bf9-7777-adac-5fb26ab7efb0" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityPeriodIncreaseDecrease_019ef5c0-0bf9-7edd-91af-03d1ce9cfc2a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquityPeriodIncreaseDecrease"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueDividendReinvestmentPlan_019ef5c0-0bf9-7408-9065-bcf7e658d5c3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodValueDividendReinvestmentPlan"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquityPeriodIncreaseDecrease_019ef5c0-0bf9-7edd-91af-03d1ce9cfc2a" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueDividendReinvestmentPlan_019ef5c0-0bf9-7408-9065-bcf7e658d5c3" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gbdc4_InvestmentCompanyDividendDistributionFromDistributableEarningsLosses_019ef5c0-0bf9-78d2-bd14-ce929d986037" xlink:href="gbdc4-20250930.xsd#gbdc4_InvestmentCompanyDividendDistributionFromDistributableEarningsLosses"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquityPeriodIncreaseDecrease_019ef5c0-0bf9-7edd-91af-03d1ce9cfc2a" xlink:to="loc_gbdc4_InvestmentCompanyDividendDistributionFromDistributableEarningsLosses_019ef5c0-0bf9-78d2-bd14-ce929d986037" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gbdc4_InvestmentCompanyDistributionDeclaredAndPayable_019ef5c0-0bf9-7200-add8-b0a50c01efa2" xlink:href="gbdc4-20250930.xsd#gbdc4_InvestmentCompanyDistributionDeclaredAndPayable"/>
    <link:calculationArc order="3" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquityPeriodIncreaseDecrease_019ef5c0-0bf9-7edd-91af-03d1ce9cfc2a" xlink:to="loc_gbdc4_InvestmentCompanyDistributionDeclaredAndPayable_019ef5c0-0bf9-7200-add8-b0a50c01efa2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingBeforeTax_019ef5c0-0bf9-7cbe-836f-ddfbbcb5006f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingBeforeTax"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquityPeriodIncreaseDecrease_019ef5c0-0bf9-7edd-91af-03d1ce9cfc2a" xlink:to="loc_us-gaap_RealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingBeforeTax_019ef5c0-0bf9-7cbe-836f-ddfbbcb5006f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingBeforeTax_019ef5c0-0bf9-731c-90b1-f0af3a160889" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingBeforeTax"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquityPeriodIncreaseDecrease_019ef5c0-0bf9-7edd-91af-03d1ce9cfc2a" xlink:to="loc_us-gaap_UnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingBeforeTax_019ef5c0-0bf9-731c-90b1-f0af3a160889" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIncomeOperatingAfterExpenseAndTax_019ef5c0-0bf9-7a72-b255-a5cdadeee6dd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentIncomeOperatingAfterExpenseAndTax"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquityPeriodIncreaseDecrease_019ef5c0-0bf9-7edd-91af-03d1ce9cfc2a" xlink:to="loc_us-gaap_InvestmentIncomeOperatingAfterExpenseAndTax_019ef5c0-0bf9-7a72-b255-a5cdadeee6dd" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_019ef5c0-0bf9-73c3-ae11-5276c5371ddc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquityPeriodIncreaseDecrease_019ef5c0-0bf9-7edd-91af-03d1ce9cfc2a" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_019ef5c0-0bf9-73c3-ae11-5276c5371ddc" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://golubcapitalbdc.com/role/ConsolidatedStatementsofCashFlows" xlink:type="simple" xlink:href="gbdc4-20250930.xsd#ConsolidatedStatementsofCashFlows"/>
  <link:calculationLink xlink:role="http://golubcapitalbdc.com/role/ConsolidatedStatementsofCashFlows" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019ef5c0-0bf9-7daf-9e9a-8a1b0483012f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfLongTermDebt_019ef5c0-0bf9-7281-b518-7dad5013aba2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromIssuanceOfLongTermDebt"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019ef5c0-0bf9-7daf-9e9a-8a1b0483012f" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfLongTermDebt_019ef5c0-0bf9-7281-b518-7dad5013aba2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLongTermDebt_019ef5c0-0bf9-790a-b706-16844da15bc6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RepaymentsOfLongTermDebt"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019ef5c0-0bf9-7daf-9e9a-8a1b0483012f" xlink:to="loc_us-gaap_RepaymentsOfLongTermDebt_019ef5c0-0bf9-790a-b706-16844da15bc6" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromOtherShortTermDebt_019ef5c0-0bf9-7a7c-9140-65d39a1ee921" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromOtherShortTermDebt"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019ef5c0-0bf9-7daf-9e9a-8a1b0483012f" xlink:to="loc_us-gaap_ProceedsFromOtherShortTermDebt_019ef5c0-0bf9-7a7c-9140-65d39a1ee921" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfOtherShortTermDebt_019ef5c0-0bf9-7195-91b8-53fd1af5bd0b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RepaymentsOfOtherShortTermDebt"/>
    <link:calculationArc order="4" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019ef5c0-0bf9-7daf-9e9a-8a1b0483012f" xlink:to="loc_us-gaap_RepaymentsOfOtherShortTermDebt_019ef5c0-0bf9-7195-91b8-53fd1af5bd0b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfDebtIssuanceCosts_019ef5c0-0bf9-7d43-b53e-11908c989f61" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsOfDebtIssuanceCosts"/>
    <link:calculationArc order="5" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019ef5c0-0bf9-7daf-9e9a-8a1b0483012f" xlink:to="loc_us-gaap_PaymentsOfDebtIssuanceCosts_019ef5c0-0bf9-7d43-b53e-11908c989f61" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gbdc4_IncreaseDecreaseInDeferredOfferingCosts_019ef5c0-0bf9-7da1-8f39-91ebd3921c7b" xlink:href="gbdc4-20250930.xsd#gbdc4_IncreaseDecreaseInDeferredOfferingCosts"/>
    <link:calculationArc order="6" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019ef5c0-0bf9-7daf-9e9a-8a1b0483012f" xlink:to="loc_gbdc4_IncreaseDecreaseInDeferredOfferingCosts_019ef5c0-0bf9-7da1-8f39-91ebd3921c7b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_019ef5c0-0bf9-75ea-b9d2-ed878ba53cad" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromIssuanceOfCommonStock"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019ef5c0-0bf9-7daf-9e9a-8a1b0483012f" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_019ef5c0-0bf9-75ea-b9d2-ed878ba53cad" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfDividendsCommonStock_019ef5c0-0bf9-7fee-bc95-559eb70b2658" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsOfDividendsCommonStock"/>
    <link:calculationArc order="8" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019ef5c0-0bf9-7daf-9e9a-8a1b0483012f" xlink:to="loc_us-gaap_PaymentsOfDividendsCommonStock_019ef5c0-0bf9-7fee-bc95-559eb70b2658" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect_019ef5c0-0bf9-7893-9cf6-8fc757da4a3d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef5c0-0bf9-704d-9778-08153d7c515c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect_019ef5c0-0bf9-7893-9cf6-8fc757da4a3d" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef5c0-0bf9-704d-9778-08153d7c515c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019ef5c0-0bf9-7ed5-8a54-703795a57a0a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect_019ef5c0-0bf9-7893-9cf6-8fc757da4a3d" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019ef5c0-0bf9-7ed5-8a54-703795a57a0a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef5c0-0bf9-7d86-8b71-e947498ee4fb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccretionAmortizationOfDiscountsAndPremiumsInvestments_019ef5c0-0bf9-7370-8239-6399f5738a73" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccretionAmortizationOfDiscountsAndPremiumsInvestments"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef5c0-0bf9-7d86-8b71-e947498ee4fb" xlink:to="loc_us-gaap_AccretionAmortizationOfDiscountsAndPremiumsInvestments_019ef5c0-0bf9-7370-8239-6399f5738a73" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities_019ef5c0-0bf9-7f29-925f-39807f339fe7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef5c0-0bf9-7d86-8b71-e947498ee4fb" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities_019ef5c0-0bf9-7f29-925f-39807f339fe7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromDispositionOfInvestmentOperatingActivity_019ef5c0-0bf9-7bcc-bea9-f11feb4bf84d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromDispositionOfInvestmentOperatingActivity"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef5c0-0bf9-7d86-8b71-e947498ee4fb" xlink:to="loc_us-gaap_ProceedsFromDispositionOfInvestmentOperatingActivity_019ef5c0-0bf9-7bcc-bea9-f11feb4bf84d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gbdc4_NonCashDividendsCapitalized_019ef5c0-0bf9-7796-ae93-dcf3087fcb0d" xlink:href="gbdc4-20250930.xsd#gbdc4_NonCashDividendsCapitalized"/>
    <link:calculationArc order="4" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef5c0-0bf9-7d86-8b71-e947498ee4fb" xlink:to="loc_gbdc4_NonCashDividendsCapitalized_019ef5c0-0bf9-7796-ae93-dcf3087fcb0d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_019ef5c0-0bf9-7b2e-9bdf-1fcec95b3dee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInOtherOperatingAssets"/>
    <link:calculationArc order="5" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef5c0-0bf9-7d86-8b71-e947498ee4fb" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_019ef5c0-0bf9-7b2e-9bdf-1fcec95b3dee" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInInterestPayableNet_019ef5c0-0bf9-70d7-9e47-546a6a0706b1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInInterestPayableNet"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef5c0-0bf9-7d86-8b71-e947498ee4fb" xlink:to="loc_us-gaap_IncreaseDecreaseInInterestPayableNet_019ef5c0-0bf9-70d7-9e47-546a6a0706b1" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccruedInterestReceivableNet_019ef5c0-0bf9-73be-8012-f9267526cbb6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInAccruedInterestReceivableNet"/>
    <link:calculationArc order="7" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef5c0-0bf9-7d86-8b71-e947498ee4fb" xlink:to="loc_us-gaap_IncreaseDecreaseInAccruedInterestReceivableNet_019ef5c0-0bf9-73be-8012-f9267526cbb6" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInManagementAndIncentiveFeesPayable_019ef5c0-0bf9-7f19-bab9-a7dec8f82b06" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInManagementAndIncentiveFeesPayable"/>
    <link:calculationArc order="8" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef5c0-0bf9-7d86-8b71-e947498ee4fb" xlink:to="loc_us-gaap_IncreaseDecreaseInManagementAndIncentiveFeesPayable_019ef5c0-0bf9-7f19-bab9-a7dec8f82b06" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gbdc4_ProceedsFromPurchasesForUndrawnPortionOfRevolvingLoansOperatingActivities_019ef5c0-0bf9-74d7-93a5-c3e4565a1e1f" xlink:href="gbdc4-20250930.xsd#gbdc4_ProceedsFromPurchasesForUndrawnPortionOfRevolvingLoansOperatingActivities"/>
    <link:calculationArc order="9" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef5c0-0bf9-7d86-8b71-e947498ee4fb" xlink:to="loc_gbdc4_ProceedsFromPurchasesForUndrawnPortionOfRevolvingLoansOperatingActivities_019ef5c0-0bf9-74d7-93a5-c3e4565a1e1f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForPurchaseOfInvestmentOperatingActivity_019ef5c0-0bf9-79e3-b8b2-6131ef9ca87c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsForPurchaseOfInvestmentOperatingActivity"/>
    <link:calculationArc order="10" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef5c0-0bf9-7d86-8b71-e947498ee4fb" xlink:to="loc_us-gaap_PaymentsForPurchaseOfInvestmentOperatingActivity_019ef5c0-0bf9-79e3-b8b2-6131ef9ca87c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyTransactionGainLossUnrealized_019ef5c0-0bf9-7ed4-8acb-e0ff1fa8d526" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignCurrencyTransactionGainLossUnrealized"/>
    <link:calculationArc order="11" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef5c0-0bf9-7d86-8b71-e947498ee4fb" xlink:to="loc_us-gaap_ForeignCurrencyTransactionGainLossUnrealized_019ef5c0-0bf9-7ed4-8acb-e0ff1fa8d526" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019ef5c0-0bf9-79b0-a57d-79e06112d63e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:calculationArc order="12" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef5c0-0bf9-7d86-8b71-e947498ee4fb" xlink:to="loc_us-gaap_NetIncomeLoss_019ef5c0-0bf9-79b0-a57d-79e06112d63e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gbdc4_InterestIncomeOperatingPaidInKindCapitalized_019ef5c0-0bf9-765d-bbf0-72951a664b39" xlink:href="gbdc4-20250930.xsd#gbdc4_InterestIncomeOperatingPaidInKindCapitalized"/>
    <link:calculationArc order="13" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef5c0-0bf9-7d86-8b71-e947498ee4fb" xlink:to="loc_gbdc4_InterestIncomeOperatingPaidInKindCapitalized_019ef5c0-0bf9-765d-bbf0-72951a664b39" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss_019ef5c0-0bf9-7e40-a33e-f2ea1b2dad24" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss"/>
    <link:calculationArc order="14" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef5c0-0bf9-7d86-8b71-e947498ee4fb" xlink:to="loc_us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss_019ef5c0-0bf9-7e40-a33e-f2ea1b2dad24" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfFinancingCosts_019ef5c0-0bf9-7dea-9f6e-b1d5c4b12bf9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AmortizationOfFinancingCosts"/>
    <link:calculationArc order="15" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef5c0-0bf9-7d86-8b71-e947498ee4fb" xlink:to="loc_us-gaap_AmortizationOfFinancingCosts_019ef5c0-0bf9-7dea-9f6e-b1d5c4b12bf9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyTransactionGainLossRealized_019ef5c0-0bf9-799d-b614-fb441b45e2a8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignCurrencyTransactionGainLossRealized"/>
    <link:calculationArc order="16" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef5c0-0bf9-7d86-8b71-e947498ee4fb" xlink:to="loc_us-gaap_ForeignCurrencyTransactionGainLossRealized_019ef5c0-0bf9-799d-b614-fb441b45e2a8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtAndEquitySecuritiesRealizedGainLoss_019ef5c0-0bf9-794e-a569-0c61fe0865ca" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtAndEquitySecuritiesRealizedGainLoss"/>
    <link:calculationArc order="17" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef5c0-0bf9-7d86-8b71-e947498ee4fb" xlink:to="loc_us-gaap_DebtAndEquitySecuritiesRealizedGainLoss_019ef5c0-0bf9-794e-a569-0c61fe0865ca" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gbdc4_IncreaseDecreaseInAccruedTrusteeFees_019ef5c0-0bf9-7d28-a72d-5d1628c32aa1" xlink:href="gbdc4-20250930.xsd#gbdc4_IncreaseDecreaseInAccruedTrusteeFees"/>
    <link:calculationArc order="18" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef5c0-0bf9-7d86-8b71-e947498ee4fb" xlink:to="loc_gbdc4_IncreaseDecreaseInAccruedTrusteeFees_019ef5c0-0bf9-7d28-a72d-5d1628c32aa1" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gbdc4_AmortizationOfDeferredOfferingCosts_019ef5c0-0bf9-7624-a056-92ff096b8a9c" xlink:href="gbdc4-20250930.xsd#gbdc4_AmortizationOfDeferredOfferingCosts"/>
    <link:calculationArc order="19" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef5c0-0bf9-7d86-8b71-e947498ee4fb" xlink:to="loc_gbdc4_AmortizationOfDeferredOfferingCosts_019ef5c0-0bf9-7624-a056-92ff096b8a9c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInReceivableForInvestmentSold_019ef5c0-0bf9-7408-9846-d59593704b93" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInReceivableForInvestmentSold"/>
    <link:calculationArc order="20" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef5c0-0bf9-7d86-8b71-e947498ee4fb" xlink:to="loc_us-gaap_IncreaseDecreaseInReceivableForInvestmentSold_019ef5c0-0bf9-7408-9846-d59593704b93" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrealizedGainLossOnDerivatives_019ef5c0-0bf9-7bd0-80c1-2a666eb6a973" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnrealizedGainLossOnDerivatives"/>
    <link:calculationArc order="21" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef5c0-0bf9-7d86-8b71-e947498ee4fb" xlink:to="loc_us-gaap_UnrealizedGainLossOnDerivatives_019ef5c0-0bf9-7bd0-80c1-2a666eb6a973" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gbdc4_ProceedsFromNonCashDividends_019ef5c0-0bf9-7bde-b24d-43014c682f7d" xlink:href="gbdc4-20250930.xsd#gbdc4_ProceedsFromNonCashDividends"/>
    <link:calculationArc order="22" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef5c0-0bf9-7d86-8b71-e947498ee4fb" xlink:to="loc_gbdc4_ProceedsFromNonCashDividends_019ef5c0-0bf9-7bde-b24d-43014c682f7d" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://golubcapitalbdc.com/role/ConsolidatedStatementsofCashFlowsParenthetical" xlink:type="simple" xlink:href="gbdc4-20250930.xsd#ConsolidatedStatementsofCashFlowsParenthetical"/>
  <link:calculationLink xlink:role="http://golubcapitalbdc.com/role/ConsolidatedStatementsofCashFlowsParenthetical" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019ef5c0-0bf9-7fd4-8c02-a9d784af7592" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalents_019ef5c0-0bf9-7726-859a-2be4c659fa4c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestrictedCashAndCashEquivalents"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019ef5c0-0bf9-7fd4-8c02-a9d784af7592" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalents_019ef5c0-0bf9-7726-859a-2be4c659fa4c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019ef5c0-0bf9-76c7-bb26-a3f8076bd477" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019ef5c0-0bf9-7fd4-8c02-a9d784af7592" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019ef5c0-0bf9-76c7-bb26-a3f8076bd477" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashHeldInForeignCurrency_019ef5c0-0bf9-7240-bed7-cea92a6a2db6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashHeldInForeignCurrency"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019ef5c0-0bf9-7fd4-8c02-a9d784af7592" xlink:to="loc_us-gaap_CashHeldInForeignCurrency_019ef5c0-0bf9-7240-bed7-cea92a6a2db6" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gbdc4_RestrictedCashHeldInForeignCurrency_019ef5c0-0bf9-76dd-886a-7c4fcd1d9883" xlink:href="gbdc4-20250930.xsd#gbdc4_RestrictedCashHeldInForeignCurrency"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019ef5c0-0bf9-7fd4-8c02-a9d784af7592" xlink:to="loc_gbdc4_RestrictedCashHeldInForeignCurrency_019ef5c0-0bf9-76dd-886a-7c4fcd1d9883" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://golubcapitalbdc.com/role/DerivativesScheduleofForwardCurrencyContractFairValueDetails" xlink:type="simple" xlink:href="gbdc4-20250930.xsd#DerivativesScheduleofForwardCurrencyContractFairValueDetails"/>
  <link:calculationLink xlink:role="http://golubcapitalbdc.com/role/DerivativesScheduleofForwardCurrencyContractFairValueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilities_019ef5c0-0bfa-7fdc-99fb-dba5f55350ef" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLiabilities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_019ef5c0-0bfa-7133-bc51-c5eb68f390fc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeFairValueOfDerivativeLiability"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DerivativeLiabilities_019ef5c0-0bfa-7fdc-99fb-dba5f55350ef" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_019ef5c0-0bfa-7133-bc51-c5eb68f390fc" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_019ef5c0-0bfa-7572-9de2-38c94f424fbe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeFairValueOfDerivativeAsset"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DerivativeLiabilities_019ef5c0-0bfa-7fdc-99fb-dba5f55350ef" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_019ef5c0-0bfa-7572-9de2-38c94f424fbe" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral_019ef5c0-0bfa-7c5b-8fc4-732a160d71fb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilities_019ef5c0-0bfa-72eb-9f9a-e254e4c4b506" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLiabilities"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral_019ef5c0-0bfa-7c5b-8fc4-732a160d71fb" xlink:to="loc_us-gaap_DerivativeLiabilities_019ef5c0-0bfa-72eb-9f9a-e254e4c4b506" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeCollateralRightToReclaimCash_019ef5c0-0bfa-795b-b168-f44f373f534c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeCollateralRightToReclaimCash"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral_019ef5c0-0bfa-7c5b-8fc4-732a160d71fb" xlink:to="loc_us-gaap_DerivativeCollateralRightToReclaimCash_019ef5c0-0bfa-795b-b168-f44f373f534c" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://golubcapitalbdc.com/role/FairValueMeasurementsScheduleofFairValueAssetsMeasuredonRecurringBasisDetails" xlink:type="simple" xlink:href="gbdc4-20250930.xsd#FairValueMeasurementsScheduleofFairValueAssetsMeasuredonRecurringBasisDetails"/>
  <link:calculationLink xlink:role="http://golubcapitalbdc.com/role/FairValueMeasurementsScheduleofFairValueAssetsMeasuredonRecurringBasisDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_019ef5c0-0bfa-7565-a3ff-110698443d71" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentOwnedAtFairValue_019ef5c0-0bfa-7b68-9e83-c31e2f3b4daf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentOwnedAtFairValue"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsFairValueDisclosure_019ef5c0-0bfa-7565-a3ff-110698443d71" xlink:to="loc_us-gaap_InvestmentOwnedAtFairValue_019ef5c0-0bfa-7b68-9e83-c31e2f3b4daf" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_019ef5c0-0bfa-7fa1-9276-31cdf17ba80f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsFairValueDisclosure_019ef5c0-0bfa-7565-a3ff-110698443d71" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_019ef5c0-0bfa-7fa1-9276-31cdf17ba80f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosure_019ef5c0-0bfa-74e1-a911-4571784fa052" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesFairValueDisclosure"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyContractsLiabilityFairValueDisclosure_019ef5c0-0bfa-7a14-9927-0c0a064ccc01" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignCurrencyContractsLiabilityFairValueDisclosure"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosure_019ef5c0-0bfa-74e1-a911-4571784fa052" xlink:to="loc_us-gaap_ForeignCurrencyContractsLiabilityFairValueDisclosure_019ef5c0-0bfa-7a14-9927-0c0a064ccc01" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://golubcapitalbdc.com/role/BorrowingsScheduleofDebtSecuritizationDetails" xlink:type="simple" xlink:href="gbdc4-20250930.xsd#BorrowingsScheduleofDebtSecuritizationDetails"/>
  <link:calculationLink xlink:role="http://golubcapitalbdc.com/role/BorrowingsScheduleofDebtSecuritizationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebt_019ef5c0-0bfa-75d3-a970-51d74df3af71" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestExpenseDebt"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfFinancingCosts_019ef5c0-0bfa-7e6f-a803-7d705b529a51" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AmortizationOfFinancingCosts"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InterestExpenseDebt_019ef5c0-0bfa-75d3-a970-51d74df3af71" xlink:to="loc_us-gaap_AmortizationOfFinancingCosts_019ef5c0-0bfa-7e6f-a803-7d705b529a51" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gbdc4_FacilityFees_019ef5c0-0bfa-7f4a-a3a3-9c27bdeef4bc" xlink:href="gbdc4-20250930.xsd#gbdc4_FacilityFees"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InterestExpenseDebt_019ef5c0-0bfa-75d3-a970-51d74df3af71" xlink:to="loc_gbdc4_FacilityFees_019ef5c0-0bfa-7f4a-a3a3-9c27bdeef4bc" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebtExcludingAmortization_019ef5c0-0bfa-774a-a461-c6cb2b0a7773" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestExpenseDebtExcludingAmortization"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InterestExpenseDebt_019ef5c0-0bfa-75d3-a970-51d74df3af71" xlink:to="loc_us-gaap_InterestExpenseDebtExcludingAmortization_019ef5c0-0bfa-774a-a461-c6cb2b0a7773" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://golubcapitalbdc.com/role/BorrowingsScheduleofMaturitiesofLongTermDebtDetails" xlink:type="simple" xlink:href="gbdc4-20250930.xsd#BorrowingsScheduleofMaturitiesofLongTermDebtDetails"/>
  <link:calculationLink xlink:role="http://golubcapitalbdc.com/role/BorrowingsScheduleofMaturitiesofLongTermDebtDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_019ef5c0-0bfa-79a1-8cd5-8bf5bf023647" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:loc xlink:type="locator" xlink:label="loc_gbdc4_LongTermDebtGrossMaturityMoreThan5Years_019ef5c0-0bfa-7462-9293-d549bac84a28" xlink:href="gbdc4-20250930.xsd#gbdc4_LongTermDebtGrossMaturityMoreThan5Years"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DebtInstrumentCarryingAmount_019ef5c0-0bfa-79a1-8cd5-8bf5bf023647" xlink:to="loc_gbdc4_LongTermDebtGrossMaturityMoreThan5Years_019ef5c0-0bfa-7462-9293-d549bac84a28" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gbdc4_LongTermDebtGrossMaturityLessThan1Year_019ef5c0-0bfa-70e7-a388-8a061d2c7f6c" xlink:href="gbdc4-20250930.xsd#gbdc4_LongTermDebtGrossMaturityLessThan1Year"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DebtInstrumentCarryingAmount_019ef5c0-0bfa-79a1-8cd5-8bf5bf023647" xlink:to="loc_gbdc4_LongTermDebtGrossMaturityLessThan1Year_019ef5c0-0bfa-70e7-a388-8a061d2c7f6c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gbdc4_LongTermDebtGrossMaturity3Through5Years_019ef5c0-0bfa-729f-80fb-b4099de88e8c" xlink:href="gbdc4-20250930.xsd#gbdc4_LongTermDebtGrossMaturity3Through5Years"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DebtInstrumentCarryingAmount_019ef5c0-0bfa-79a1-8cd5-8bf5bf023647" xlink:to="loc_gbdc4_LongTermDebtGrossMaturity3Through5Years_019ef5c0-0bfa-729f-80fb-b4099de88e8c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gbdc4_LongTermDebtGrossMaturity1Through3Years_019ef5c0-0bfa-7a9c-acc3-a66da66b80a5" xlink:href="gbdc4-20250930.xsd#gbdc4_LongTermDebtGrossMaturity1Through3Years"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DebtInstrumentCarryingAmount_019ef5c0-0bfa-79a1-8cd5-8bf5bf023647" xlink:to="loc_gbdc4_LongTermDebtGrossMaturity1Through3Years_019ef5c0-0bfa-7a9c-acc3-a66da66b80a5" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://golubcapitalbdc.com/role/FederalIncomeTaxMattersScheduleofNetIncreaseinNetAssetsResultingfromOperationstoTaxableIncomeDetails" xlink:type="simple" xlink:href="gbdc4-20250930.xsd#FederalIncomeTaxMattersScheduleofNetIncreaseinNetAssetsResultingfromOperationstoTaxableIncomeDetails"/>
  <link:calculationLink xlink:role="http://golubcapitalbdc.com/role/FederalIncomeTaxMattersScheduleofNetIncreaseinNetAssetsResultingfromOperationstoTaxableIncomeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyTaxBasisTaxableIncomeLossBeforeDeductionForDistribution_019ef5c0-0bfa-7706-a7c1-d71358e72137" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyTaxBasisTaxableIncomeLossBeforeDeductionForDistribution"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyTaxBasisOtherIncreaseDecrease_019ef5c0-0bfa-7c49-a554-d65fb3e6f580" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyTaxBasisOtherIncreaseDecrease"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentCompanyTaxBasisTaxableIncomeLossBeforeDeductionForDistribution_019ef5c0-0bfa-7706-a7c1-d71358e72137" xlink:to="loc_us-gaap_InvestmentCompanyTaxBasisOtherIncreaseDecrease_019ef5c0-0bfa-7c49-a554-d65fb3e6f580" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyTaxBasisIncomeNotCurrentlyTaxable_019ef5c0-0bfa-7d5b-9a68-e5e3936abdba" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyTaxBasisIncomeNotCurrentlyTaxable"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentCompanyTaxBasisTaxableIncomeLossBeforeDeductionForDistribution_019ef5c0-0bfa-7706-a7c1-d71358e72137" xlink:to="loc_us-gaap_InvestmentCompanyTaxBasisIncomeNotCurrentlyTaxable_019ef5c0-0bfa-7d5b-9a68-e5e3936abdba" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyTaxBasisExpenseDeductible_019ef5c0-0bfa-7391-ae2e-bf6e23dced19" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyTaxBasisExpenseDeductible"/>
    <link:calculationArc order="3" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentCompanyTaxBasisTaxableIncomeLossBeforeDeductionForDistribution_019ef5c0-0bfa-7706-a7c1-d71358e72137" xlink:to="loc_us-gaap_InvestmentCompanyTaxBasisExpenseDeductible_019ef5c0-0bfa-7391-ae2e-bf6e23dced19" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019ef5c0-0bfa-7900-b1a6-2fc31b237eff" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentCompanyTaxBasisTaxableIncomeLossBeforeDeductionForDistribution_019ef5c0-0bfa-7706-a7c1-d71358e72137" xlink:to="loc_us-gaap_NetIncomeLoss_019ef5c0-0bfa-7900-b1a6-2fc31b237eff" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyTaxBasisUnrealizedGainLossNotCurrentlyTaxableDeductible_019ef5c0-0bfa-7864-b4ab-84f07bf03123" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyTaxBasisUnrealizedGainLossNotCurrentlyTaxableDeductible"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentCompanyTaxBasisTaxableIncomeLossBeforeDeductionForDistribution_019ef5c0-0bfa-7706-a7c1-d71358e72137" xlink:to="loc_us-gaap_InvestmentCompanyTaxBasisUnrealizedGainLossNotCurrentlyTaxableDeductible_019ef5c0-0bfa-7864-b4ab-84f07bf03123" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyTaxBasisExpenseNotCurrentlyDeductible_019ef5c0-0bfa-7343-bdfa-59c65d467284" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyTaxBasisExpenseNotCurrentlyDeductible"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentCompanyTaxBasisTaxableIncomeLossBeforeDeductionForDistribution_019ef5c0-0bfa-7706-a7c1-d71358e72137" xlink:to="loc_us-gaap_InvestmentCompanyTaxBasisExpenseNotCurrentlyDeductible_019ef5c0-0bfa-7343-bdfa-59c65d467284" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyTaxBasisIncomeTaxable_019ef5c0-0bfa-758e-bf15-a03a7dd42b3b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyTaxBasisIncomeTaxable"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentCompanyTaxBasisTaxableIncomeLossBeforeDeductionForDistribution_019ef5c0-0bfa-7706-a7c1-d71358e72137" xlink:to="loc_us-gaap_InvestmentCompanyTaxBasisIncomeTaxable_019ef5c0-0bfa-758e-bf15-a03a7dd42b3b" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://golubcapitalbdc.com/role/FederalIncomeTaxMattersScheduleofAccumulatedEarningsDeficitBookBasisIncomeTaxDetails" xlink:type="simple" xlink:href="gbdc4-20250930.xsd#FederalIncomeTaxMattersScheduleofAccumulatedEarningsDeficitBookBasisIncomeTaxDetails"/>
  <link:calculationLink xlink:role="http://golubcapitalbdc.com/role/FederalIncomeTaxMattersScheduleofAccumulatedEarningsDeficitBookBasisIncomeTaxDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_019ef5c0-0bfa-79de-9b69-9679f59193df" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyDistributableEarningsLossAccumulatedOrdinaryIncomeLoss_019ef5c0-0bfa-787e-a545-150e0536088d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyDistributableEarningsLossAccumulatedOrdinaryIncomeLoss"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_RetainedEarningsAccumulatedDeficit_019ef5c0-0bfa-79de-9b69-9679f59193df" xlink:to="loc_us-gaap_InvestmentCompanyDistributableEarningsLossAccumulatedOrdinaryIncomeLoss_019ef5c0-0bfa-787e-a545-150e0536088d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyDistributableEarningsLossAccumulatedAppreciationDepreciation_019ef5c0-0bfa-776a-9f89-460eac0a55eb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyDistributableEarningsLossAccumulatedAppreciationDepreciation"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_RetainedEarningsAccumulatedDeficit_019ef5c0-0bfa-79de-9b69-9679f59193df" xlink:to="loc_us-gaap_InvestmentCompanyDistributableEarningsLossAccumulatedAppreciationDepreciation_019ef5c0-0bfa-776a-9f89-460eac0a55eb" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gbdc4_InvestmentCompanyDistributableEarningsLossAccumulatedOtherTemporaryDifferences_019ef5c0-0bfa-7ec5-8aec-365c8b072bfa" xlink:href="gbdc4-20250930.xsd#gbdc4_InvestmentCompanyDistributableEarningsLossAccumulatedOtherTemporaryDifferences"/>
    <link:calculationArc order="3" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_RetainedEarningsAccumulatedDeficit_019ef5c0-0bfa-79de-9b69-9679f59193df" xlink:to="loc_gbdc4_InvestmentCompanyDistributableEarningsLossAccumulatedOtherTemporaryDifferences_019ef5c0-0bfa-7ec5-8aec-365c8b072bfa" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyDistributableEarningsLossAccumulatedLongTermCapitalGainLoss_019ef5c0-0bfa-7944-89c4-507437fd6ba4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyDistributableEarningsLossAccumulatedLongTermCapitalGainLoss"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_RetainedEarningsAccumulatedDeficit_019ef5c0-0bfa-79de-9b69-9679f59193df" xlink:to="loc_us-gaap_InvestmentCompanyDistributableEarningsLossAccumulatedLongTermCapitalGainLoss_019ef5c0-0bfa-7944-89c4-507437fd6ba4" xlink:type="arc"/>
  </link:calculationLink>
</link:linkbase>
