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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019e474a-bb1f-7eb0-ad77-7d6d09274ac2,g:9fac9124-df97-439d-8da9-20798a4b8882-->
<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://www.gladstoneinvestment.com/role/CONSOLIDATEDSTATEMENTSOFASSETSANDLIABILITIES" xlink:type="simple" xlink:href="gain-20260630.xsd#CONSOLIDATEDSTATEMENTSOFASSETSANDLIABILITIES"/>
  <link:calculationLink xlink:role="http://www.gladstoneinvestment.com/role/CONSOLIDATEDSTATEMENTSOFASSETSANDLIABILITIES" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019e474a-bfe2-75cf-a71c-8dd8e0fc5750" 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_AdditionalPaidInCapital_019e474a-bfe2-741c-a51f-1e90f8627269" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.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_019e474a-bfe2-75cf-a71c-8dd8e0fc5750" xlink:to="loc_us-gaap_AdditionalPaidInCapital_019e474a-bfe2-741c-a51f-1e90f8627269" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_019e474a-bfe2-748e-a18e-1486d58e43ea" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_019e474a-bfe2-75cf-a71c-8dd8e0fc5750" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_019e474a-bfe2-748e-a18e-1486d58e43ea" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValue_019e474a-bfe2-783e-9f98-3088e7686d89" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.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_019e474a-bfe2-75cf-a71c-8dd8e0fc5750" xlink:to="loc_us-gaap_CommonStockValue_019e474a-bfe2-783e-9f98-3088e7686d89" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_019e474a-bfe2-7c54-8c21-e198dee83587" 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_InvestmentOwnedAtFairValue_019e474a-bfe2-7d05-99e8-97a79cb5111e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.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_019e474a-bfe2-7c54-8c21-e198dee83587" xlink:to="loc_us-gaap_InvestmentOwnedAtFairValue_019e474a-bfe2-7d05-99e8-97a79cb5111e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Cash_019e474a-bfe2-72a4-907a-5a9621642fcd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Cash"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019e474a-bfe2-7c54-8c21-e198dee83587" xlink:to="loc_us-gaap_Cash_019e474a-bfe2-72a4-907a-5a9621642fcd" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MoneyMarketFundsAtCarryingValue_019e474a-bfe2-7f34-b74c-b3931b35b045" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MoneyMarketFundsAtCarryingValue"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019e474a-bfe2-7c54-8c21-e198dee83587" xlink:to="loc_us-gaap_MoneyMarketFundsAtCarryingValue_019e474a-bfe2-7f34-b74c-b3931b35b045" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCash_019e474a-bfe2-7b82-9cbf-3020559ed29a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedCash"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019e474a-bfe2-7c54-8c21-e198dee83587" xlink:to="loc_us-gaap_RestrictedCash_019e474a-bfe2-7b82-9cbf-3020559ed29a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestReceivable_019e474a-bfe2-7be9-9edd-82c26ff7d75d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestReceivable"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019e474a-bfe2-7c54-8c21-e198dee83587" xlink:to="loc_us-gaap_InterestReceivable_019e474a-bfe2-7be9-9edd-82c26ff7d75d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherReceivables_019e474a-bfe2-7f99-afb2-d5f9fce56320" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherReceivables"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019e474a-bfe2-7c54-8c21-e198dee83587" xlink:to="loc_us-gaap_OtherReceivables_019e474a-bfe2-7f99-afb2-d5f9fce56320" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNet_019e474a-bfe2-78d5-b6dc-c57e8b87ddb7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredFinanceCostsNet"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019e474a-bfe2-7c54-8c21-e198dee83587" xlink:to="loc_us-gaap_DeferredFinanceCostsNet_019e474a-bfe2-78d5-b6dc-c57e8b87ddb7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssets_019e474a-bfe2-72ce-8867-3615a8af39f7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherAssets"/>
    <link:calculationArc order="8" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019e474a-bfe2-7c54-8c21-e198dee83587" xlink:to="loc_us-gaap_OtherAssets_019e474a-bfe2-72ce-8867-3615a8af39f7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_019e474a-bfe2-76b0-8da2-002f55319450" 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_LineOfCredit_019e474a-bfe2-78ca-ad37-3603a22b43cb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCredit"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LongTermDebt_019e474a-bfe2-76b0-8da2-002f55319450" xlink:to="loc_us-gaap_LineOfCredit_019e474a-bfe2-78ca-ad37-3603a22b43cb" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesPayable_019e474a-bfe2-7b9c-bd3e-766085431dfe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NotesPayable"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LongTermDebt_019e474a-bfe2-76b0-8da2-002f55319450" xlink:to="loc_us-gaap_NotesPayable_019e474a-bfe2-7b9c-bd3e-766085431dfe" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsNet_019e474a-bfe2-7dc8-9a8c-770d79247dc7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetsNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_019e474a-bfe2-764c-a188-b122af08be91" 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="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsNet_019e474a-bfe2-7dc8-9a8c-770d79247dc7" xlink:to="loc_us-gaap_Liabilities_019e474a-bfe2-764c-a188-b122af08be91" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_019e474a-bfe2-7ea0-8d59-bfc158ed37c8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Assets"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsNet_019e474a-bfe2-7dc8-9a8c-770d79247dc7" xlink:to="loc_us-gaap_Assets_019e474a-bfe2-7ea0-8d59-bfc158ed37c8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingencies_019e474a-bfe2-708b-a6dd-581d561a4442" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommitmentsAndContingencies"/>
    <link:calculationArc order="3" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsNet_019e474a-bfe2-7dc8-9a8c-770d79247dc7" xlink:to="loc_us-gaap_CommitmentsAndContingencies_019e474a-bfe2-708b-a6dd-581d561a4442" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_019e474a-bfe2-700a-bd51-a9743577e7a2" 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_LongTermDebt_019e474a-bfe2-7831-8d40-f4889097d3f8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebt"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019e474a-bfe2-700a-bd51-a9743577e7a2" xlink:to="loc_us-gaap_LongTermDebt_019e474a-bfe2-7831-8d40-f4889097d3f8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent_019e474a-bfe2-7acf-96e6-42c64b6337ef" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019e474a-bfe2-700a-bd51-a9743577e7a2" xlink:to="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent_019e474a-bfe2-7acf-96e6-42c64b6337ef" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestPayableCurrentAndNoncurrent_019e474a-bfe2-79c2-ad45-31f11228aa0a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestPayableCurrentAndNoncurrent"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019e474a-bfe2-700a-bd51-a9743577e7a2" xlink:to="loc_us-gaap_InterestPayableCurrentAndNoncurrent_019e474a-bfe2-79c2-ad45-31f11228aa0a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableOtherCurrentAndNoncurrent_019e474a-bfe2-7e25-94a0-3754bc02c6d6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccountsPayableOtherCurrentAndNoncurrent"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019e474a-bfe2-700a-bd51-a9743577e7a2" xlink:to="loc_us-gaap_AccountsPayableOtherCurrentAndNoncurrent_019e474a-bfe2-7e25-94a0-3754bc02c6d6" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilities_019e474a-bfe2-79f1-a840-352706bab519" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherLiabilities"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019e474a-bfe2-700a-bd51-a9743577e7a2" xlink:to="loc_us-gaap_OtherLiabilities_019e474a-bfe2-79f1-a840-352706bab519" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.gladstoneinvestment.com/role/CONSOLIDATEDSTATEMENTSOFOPERATIONS" xlink:type="simple" xlink:href="gain-20260630.xsd#CONSOLIDATEDSTATEMENTSOFOPERATIONS"/>
  <link:calculationLink xlink:role="http://www.gladstoneinvestment.com/role/CONSOLIDATEDSTATEMENTSOFOPERATIONS" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyExpenseAfterReductionOfFeeWaiverAndReimbursement_019e474a-bfe2-7979-9b9c-0e6c72979c5e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentCompanyExpenseAfterReductionOfFeeWaiverAndReimbursement"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyVoluntaryFeeWaived_019e474a-bfe2-76c7-83df-ee927a8fe1bc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentCompanyVoluntaryFeeWaived"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentCompanyExpenseAfterReductionOfFeeWaiverAndReimbursement_019e474a-bfe2-7979-9b9c-0e6c72979c5e" xlink:to="loc_us-gaap_InvestmentCompanyVoluntaryFeeWaived_019e474a-bfe2-76c7-83df-ee927a8fe1bc" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyContractualFeeWaived_019e474a-bfe2-762a-b7be-b21f1847aedb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentCompanyContractualFeeWaived"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentCompanyExpenseAfterReductionOfFeeWaiverAndReimbursement_019e474a-bfe2-7979-9b9c-0e6c72979c5e" xlink:to="loc_us-gaap_InvestmentCompanyContractualFeeWaived_019e474a-bfe2-762a-b7be-b21f1847aedb" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIncomeInvestmentExpense_019e474a-bfe2-745f-b5f5-0824e672a7b5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentIncomeInvestmentExpense"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentCompanyExpenseAfterReductionOfFeeWaiverAndReimbursement_019e474a-bfe2-7979-9b9c-0e6c72979c5e" xlink:to="loc_us-gaap_InvestmentIncomeInvestmentExpense_019e474a-bfe2-745f-b5f5-0824e672a7b5" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealizedAndUnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionOperatingAfterTax_019e474a-bfe2-722e-8590-2a3935e58c1d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealizedAndUnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionOperatingAfterTax"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtAndEquitySecuritiesRealizedGainLoss_019e474a-bfe2-7d44-a4f8-d3537ef204f4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.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_RealizedAndUnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionOperatingAfterTax_019e474a-bfe2-722e-8590-2a3935e58c1d" xlink:to="loc_us-gaap_DebtAndEquitySecuritiesRealizedGainLoss_019e474a-bfe2-7d44-a4f8-d3537ef204f4" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss_019e474a-bfe2-7781-b2ac-8d9e043be1c3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_RealizedAndUnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionOperatingAfterTax_019e474a-bfe2-722e-8590-2a3935e58c1d" xlink:to="loc_us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss_019e474a-bfe2-7781-b2ac-8d9e043be1c3" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIncomeInvestmentExpense_019e474a-bfe2-7095-92c7-c0a3b9768651" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentIncomeInvestmentExpense"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdministrativeFeesExpense_019e474a-bfe2-76b0-8eb6-b26c845d7f07" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.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_019e474a-bfe2-7095-92c7-c0a3b9768651" xlink:to="loc_us-gaap_AdministrativeFeesExpense_019e474a-bfe2-76b0-8eb6-b26c845d7f07" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfessionalFees_019e474a-bfe2-79a5-9517-e0e1e26a5607" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProfessionalFees"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentIncomeInvestmentExpense_019e474a-bfe2-7095-92c7-c0a3b9768651" xlink:to="loc_us-gaap_ProfessionalFees_019e474a-bfe2-79a5-9517-e0e1e26a5607" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfFinancingCostsAndDiscounts_019e474a-bfe2-7e01-a487-f90b62148bda" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AmortizationOfFinancingCostsAndDiscounts"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentIncomeInvestmentExpense_019e474a-bfe2-7095-92c7-c0a3b9768651" xlink:to="loc_us-gaap_AmortizationOfFinancingCostsAndDiscounts_019e474a-bfe2-7e01-a487-f90b62148bda" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherGeneralAndAdministrativeExpense_019e474a-bfe2-7626-a875-4bc0be6eb817" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherGeneralAndAdministrativeExpense"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentIncomeInvestmentExpense_019e474a-bfe2-7095-92c7-c0a3b9768651" xlink:to="loc_us-gaap_OtherGeneralAndAdministrativeExpense_019e474a-bfe2-7626-a875-4bc0be6eb817" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoanProcessingFee_019e474a-bfe2-7d36-812d-c5559c90fe21" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LoanProcessingFee"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentIncomeInvestmentExpense_019e474a-bfe2-7095-92c7-c0a3b9768651" xlink:to="loc_us-gaap_LoanProcessingFee_019e474a-bfe2-7d36-812d-c5559c90fe21" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseBorrowings_019e474a-bfe2-7c7d-9727-7b3b79cb4fda" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestExpenseBorrowings"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentIncomeInvestmentExpense_019e474a-bfe2-7095-92c7-c0a3b9768651" xlink:to="loc_us-gaap_InterestExpenseBorrowings_019e474a-bfe2-7c7d-9727-7b3b79cb4fda" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ManagementFeeExpense_019e474a-bfe2-7afe-8a12-0eb0a8fff50b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ManagementFeeExpense"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentIncomeInvestmentExpense_019e474a-bfe2-7095-92c7-c0a3b9768651" xlink:to="loc_us-gaap_ManagementFeeExpense_019e474a-bfe2-7afe-8a12-0eb0a8fff50b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gain_NetTotalIncentiveFee_019e474a-bfe2-7a54-b626-785ecd3f1ab0" xlink:href="gain-20260630.xsd#gain_NetTotalIncentiveFee"/>
    <link:calculationArc order="8" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentIncomeInvestmentExpense_019e474a-bfe2-7095-92c7-c0a3b9768651" xlink:to="loc_gain_NetTotalIncentiveFee_019e474a-bfe2-7a54-b626-785ecd3f1ab0" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_019e474a-bfe2-7cf4-824a-d821a56118f1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProfitLoss"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetInvestmentIncome_019e474a-bfe2-73e3-95b8-2bd2f9725312" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetInvestmentIncome"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_ProfitLoss_019e474a-bfe2-7cf4-824a-d821a56118f1" xlink:to="loc_us-gaap_NetInvestmentIncome_019e474a-bfe2-73e3-95b8-2bd2f9725312" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealizedAndUnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionOperatingAfterTax_019e474a-bfe2-773d-a008-f37733469400" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealizedAndUnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionOperatingAfterTax"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_ProfitLoss_019e474a-bfe2-7cf4-824a-d821a56118f1" xlink:to="loc_us-gaap_RealizedAndUnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionOperatingAfterTax_019e474a-bfe2-773d-a008-f37733469400" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrossInvestmentIncomeOperating_019e474a-bfe2-75bf-bfa4-25a776fa413d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GrossInvestmentIncomeOperating"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendIncomeOperatingPaidInCash_019e474a-bfe2-7946-8486-ab58863511e7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DividendIncomeOperatingPaidInCash"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_GrossInvestmentIncomeOperating_019e474a-bfe2-75bf-bfa4-25a776fa413d" xlink:to="loc_us-gaap_DividendIncomeOperatingPaidInCash_019e474a-bfe2-7946-8486-ab58863511e7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FeeIncome_019e474a-bfe2-7ccf-b0e9-20e12cbdbdad" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FeeIncome"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_GrossInvestmentIncomeOperating_019e474a-bfe2-75bf-bfa4-25a776fa413d" xlink:to="loc_us-gaap_FeeIncome_019e474a-bfe2-7ccf-b0e9-20e12cbdbdad" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeOperatingPaidInCash_019e474a-bfe2-7202-924a-00f9c8d74251" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestIncomeOperatingPaidInCash"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_GrossInvestmentIncomeOperating_019e474a-bfe2-75bf-bfa4-25a776fa413d" xlink:to="loc_us-gaap_InterestIncomeOperatingPaidInCash_019e474a-bfe2-7202-924a-00f9c8d74251" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetInvestmentIncome_019e474a-bfe2-7e62-9087-6d53522dfbb7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetInvestmentIncome"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyExpenseAfterReductionOfFeeWaiverAndReimbursement_019e474a-bfe2-7274-95c7-44bc19c4e64f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.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_019e474a-bfe2-7e62-9087-6d53522dfbb7" xlink:to="loc_us-gaap_InvestmentCompanyExpenseAfterReductionOfFeeWaiverAndReimbursement_019e474a-bfe2-7274-95c7-44bc19c4e64f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrossInvestmentIncomeOperating_019e474a-bfe2-7a12-aa04-9238271a276d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.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_019e474a-bfe2-7e62-9087-6d53522dfbb7" xlink:to="loc_us-gaap_GrossInvestmentIncomeOperating_019e474a-bfe2-7a12-aa04-9238271a276d" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.gladstoneinvestment.com/role/CONSOLIDATEDSTATEMENTSOFCHANGESINNETASSETS" xlink:type="simple" xlink:href="gain-20260630.xsd#CONSOLIDATEDSTATEMENTSOFCHANGESINNETASSETS"/>
  <link:calculationLink xlink:role="http://www.gladstoneinvestment.com/role/CONSOLIDATEDSTATEMENTSOFCHANGESINNETASSETS" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyDividendDistribution_019e474a-bfe2-7776-998d-eb24cd3c3bf1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentCompanyDividendDistribution"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyDistributionLongTermCapitalGain_019e474a-bfe2-7de6-80ee-ab7b24f749fd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentCompanyDistributionLongTermCapitalGain"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentCompanyDividendDistribution_019e474a-bfe2-7776-998d-eb24cd3c3bf1" xlink:to="loc_us-gaap_InvestmentCompanyDistributionLongTermCapitalGain_019e474a-bfe2-7de6-80ee-ab7b24f749fd" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyDistributionOrdinaryIncome_019e474a-bfe2-75ae-9a38-c9ce87b9f49a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentCompanyDistributionOrdinaryIncome"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentCompanyDividendDistribution_019e474a-bfe2-7776-998d-eb24cd3c3bf1" xlink:to="loc_us-gaap_InvestmentCompanyDistributionOrdinaryIncome_019e474a-bfe2-75ae-9a38-c9ce87b9f49a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gain_InvestmentCompanyCapitalActivityIncreaseDecrease_019e474a-bfe2-79df-a321-db9ed6d241db" xlink:href="gain-20260630.xsd#gain_InvestmentCompanyCapitalActivityIncreaseDecrease"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_019e474a-bfe2-77b8-aaba-c5d9a56b0f48" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_gain_InvestmentCompanyCapitalActivityIncreaseDecrease_019e474a-bfe2-79df-a321-db9ed6d241db" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_019e474a-bfe2-77b8-aaba-c5d9a56b0f48" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalStockIssuedIssuanceCosts_019e474a-bfe2-7823-bf8e-41b6605dc33e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalStockIssuedIssuanceCosts"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_gain_InvestmentCompanyCapitalActivityIncreaseDecrease_019e474a-bfe2-79df-a321-db9ed6d241db" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalStockIssuedIssuanceCosts_019e474a-bfe2-7823-bf8e-41b6605dc33e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_019e474a-bfe2-7a01-bb3b-8f6fc68d2cf0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProfitLoss"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIncomeOperatingAfterExpenseAndTax_019e474a-bfe2-7111-96d7-210aa01eab70" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.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_ProfitLoss_019e474a-bfe2-7a01-bb3b-8f6fc68d2cf0" xlink:to="loc_us-gaap_InvestmentIncomeOperatingAfterExpenseAndTax_019e474a-bfe2-7111-96d7-210aa01eab70" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingBeforeTax_019e474a-bfe2-7770-90e5-9982f2fb13fd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingBeforeTax"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_ProfitLoss_019e474a-bfe2-7a01-bb3b-8f6fc68d2cf0" xlink:to="loc_us-gaap_RealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingBeforeTax_019e474a-bfe2-7770-90e5-9982f2fb13fd" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingBeforeTax_019e474a-bfe2-7655-9e1e-9bcee8907af6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingBeforeTax"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_ProfitLoss_019e474a-bfe2-7a01-bb3b-8f6fc68d2cf0" xlink:to="loc_us-gaap_UnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingBeforeTax_019e474a-bfe2-7655-9e1e-9bcee8907af6" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gain_UnrealizedGainLossOtherAccumulatedDepreciationAppreciationBeforeTax_019e474a-bfe2-724f-af56-e7e472a5fa0f" xlink:href="gain-20260630.xsd#gain_UnrealizedGainLossOtherAccumulatedDepreciationAppreciationBeforeTax"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_ProfitLoss_019e474a-bfe2-7a01-bb3b-8f6fc68d2cf0" xlink:to="loc_gain_UnrealizedGainLossOtherAccumulatedDepreciationAppreciationBeforeTax_019e474a-bfe2-724f-af56-e7e472a5fa0f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityPeriodIncreaseDecrease_019e474a-bfe2-7a21-b606-9406a68017fa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityPeriodIncreaseDecrease"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_019e474a-bfe2-7d65-932a-6c5a2f7cffec" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProfitLoss"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquityPeriodIncreaseDecrease_019e474a-bfe2-7a21-b606-9406a68017fa" xlink:to="loc_us-gaap_ProfitLoss_019e474a-bfe2-7d65-932a-6c5a2f7cffec" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyDividendDistribution_019e474a-bfe2-756e-b710-5d30a3261722" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentCompanyDividendDistribution"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquityPeriodIncreaseDecrease_019e474a-bfe2-7a21-b606-9406a68017fa" xlink:to="loc_us-gaap_InvestmentCompanyDividendDistribution_019e474a-bfe2-756e-b710-5d30a3261722" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gain_InvestmentCompanyCapitalActivityIncreaseDecrease_019e474a-bfe2-7472-aa71-501fddf93c4a" xlink:href="gain-20260630.xsd#gain_InvestmentCompanyCapitalActivityIncreaseDecrease"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquityPeriodIncreaseDecrease_019e474a-bfe2-7a21-b606-9406a68017fa" xlink:to="loc_gain_InvestmentCompanyCapitalActivityIncreaseDecrease_019e474a-bfe2-7472-aa71-501fddf93c4a" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.gladstoneinvestment.com/role/CONSOLIDATEDSTATEMENTSOFCASHFLOWS" xlink:type="simple" xlink:href="gain-20260630.xsd#CONSOLIDATEDSTATEMENTSOFCASHFLOWS"/>
  <link:calculationLink xlink:role="http://www.gladstoneinvestment.com/role/CONSOLIDATEDSTATEMENTSOFCASHFLOWS" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e474a-bfe2-7b9f-8bce-14d4e382d729" 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_IncreaseDecreaseInDueFromRelatedParties_019e474a-bfe2-74b9-968f-de727acce823" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInDueFromRelatedParties"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e474a-bfe2-7b9f-8bce-14d4e382d729" xlink:to="loc_us-gaap_IncreaseDecreaseInDueFromRelatedParties_019e474a-bfe2-74b9-968f-de727acce823" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInDueToRelatedParties_019e474a-bfe2-7479-9029-22bad248363b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInDueToRelatedParties"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e474a-bfe2-7b9f-8bce-14d4e382d729" xlink:to="loc_us-gaap_IncreaseDecreaseInDueToRelatedParties_019e474a-bfe2-7479-9029-22bad248363b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLossWriteoffAfterRecovery_019e474a-bfe2-7d7d-aca4-2f9c898a98e5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancingReceivableAllowanceForCreditLossWriteoffAfterRecovery"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e474a-bfe2-7b9f-8bce-14d4e382d729" xlink:to="loc_us-gaap_FinancingReceivableAllowanceForCreditLossWriteoffAfterRecovery_019e474a-bfe2-7d7d-aca4-2f9c898a98e5" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_019e474a-bfe2-74a9-8d26-d443fafac456" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInOtherOperatingAssets"/>
    <link:calculationArc order="4" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e474a-bfe2-7b9f-8bce-14d4e382d729" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_019e474a-bfe2-74a9-8d26-d443fafac456" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_019e474a-bfe2-76f3-a806-33d33e80d732" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProfitLoss"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e474a-bfe2-7b9f-8bce-14d4e382d729" xlink:to="loc_us-gaap_ProfitLoss_019e474a-bfe2-76f3-a806-33d33e80d732" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities_019e474a-bfe2-773a-bbff-3dd6de0c135a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e474a-bfe2-7b9f-8bce-14d4e382d729" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities_019e474a-bfe2-773a-bbff-3dd6de0c135a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss_019e474a-bfe2-7f1d-b03a-1f7ff1d6e802" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss"/>
    <link:calculationArc order="7" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e474a-bfe2-7b9f-8bce-14d4e382d729" xlink:to="loc_us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss_019e474a-bfe2-7f1d-b03a-1f7ff1d6e802" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtAndEquitySecuritiesRealizedGainLoss_019e474a-bfe2-7e24-98cc-1dea71b5519b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtAndEquitySecuritiesRealizedGainLoss"/>
    <link:calculationArc order="8" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e474a-bfe2-7b9f-8bce-14d4e382d729" xlink:to="loc_us-gaap_DebtAndEquitySecuritiesRealizedGainLoss_019e474a-bfe2-7e24-98cc-1dea71b5519b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_019e474a-bfe2-7d82-8073-43c00e605e2d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInOtherOperatingLiabilities"/>
    <link:calculationArc order="9" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e474a-bfe2-7b9f-8bce-14d4e382d729" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_019e474a-bfe2-7d82-8073-43c00e605e2d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForPurchaseOfInvestmentOperatingActivity_019e474a-bfe2-7932-b2c6-358a280ba0f3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.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_019e474a-bfe2-7b9f-8bce-14d4e382d729" xlink:to="loc_us-gaap_PaymentsForPurchaseOfInvestmentOperatingActivity_019e474a-bfe2-7932-b2c6-358a280ba0f3" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccruedInterestReceivableNet_019e474a-bfe2-7876-aa77-51a412ec7c79" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInAccruedInterestReceivableNet"/>
    <link:calculationArc order="11" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e474a-bfe2-7b9f-8bce-14d4e382d729" xlink:to="loc_us-gaap_IncreaseDecreaseInAccruedInterestReceivableNet_019e474a-bfe2-7876-aa77-51a412ec7c79" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gain_AmortizationOfDeferredFinancingCostsAndDiscounts_019e474a-bfe2-794e-9ba5-79d6dd91485f" xlink:href="gain-20260630.xsd#gain_AmortizationOfDeferredFinancingCostsAndDiscounts"/>
    <link:calculationArc order="12" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e474a-bfe2-7b9f-8bce-14d4e382d729" xlink:to="loc_gain_AmortizationOfDeferredFinancingCostsAndDiscounts_019e474a-bfe2-794e-9ba5-79d6dd91485f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gain_ProceedsFromPrincipalRepaymentsOfInvestmentsOperatingActivity_019e474a-bfe2-7d71-8f18-70e8584fdaaa" xlink:href="gain-20260630.xsd#gain_ProceedsFromPrincipalRepaymentsOfInvestmentsOperatingActivity"/>
    <link:calculationArc order="13" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e474a-bfe2-7b9f-8bce-14d4e382d729" xlink:to="loc_gain_ProceedsFromPrincipalRepaymentsOfInvestmentsOperatingActivity_019e474a-bfe2-7d71-8f18-70e8584fdaaa" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInInterestPayableNet_019e474a-bfe2-76d2-8e03-dfb8fe0c8596" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInInterestPayableNet"/>
    <link:calculationArc order="14" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e474a-bfe2-7b9f-8bce-14d4e382d729" xlink:to="loc_us-gaap_IncreaseDecreaseInInterestPayableNet_019e474a-bfe2-76d2-8e03-dfb8fe0c8596" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gain_ProceedsFromSaleAndRecapitalizationOfInvestmentsNetOperatingActivity_019e474a-bfe2-75e7-8564-cb1e487a5828" xlink:href="gain-20260630.xsd#gain_ProceedsFromSaleAndRecapitalizationOfInvestmentsNetOperatingActivity"/>
    <link:calculationArc order="15" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e474a-bfe2-7b9f-8bce-14d4e382d729" xlink:to="loc_gain_ProceedsFromSaleAndRecapitalizationOfInvestmentsNetOperatingActivity_019e474a-bfe2-75e7-8564-cb1e487a5828" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_019e474a-bfe2-73f1-a22d-ba84f4574a94" 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_019e474a-bfe2-79a7-9d77-db4f22c509c2" 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="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_019e474a-bfe2-73f1-a22d-ba84f4574a94" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e474a-bfe2-79a7-9d77-db4f22c509c2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019e474a-bfe2-745a-a072-de3e91cbc691" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.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_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_019e474a-bfe2-73f1-a22d-ba84f4574a94" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019e474a-bfe2-745a-a072-de3e91cbc691" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019e474a-bfe2-7df4-a596-02f193aadbf3" 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_gain_ProceedsPaymentsFromIssuanceOfCommonStockNet_019e474a-bfe2-783a-b9ba-f0fe865fb0d9" xlink:href="gain-20260630.xsd#gain_ProceedsPaymentsFromIssuanceOfCommonStockNet"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019e474a-bfe2-7df4-a596-02f193aadbf3" xlink:to="loc_gain_ProceedsPaymentsFromIssuanceOfCommonStockNet_019e474a-bfe2-783a-b9ba-f0fe865fb0d9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromLinesOfCredit_019e474a-bfe2-7fd4-93f6-1c39c7a7544e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromLinesOfCredit"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019e474a-bfe2-7df4-a596-02f193aadbf3" xlink:to="loc_us-gaap_ProceedsFromLinesOfCredit_019e474a-bfe2-7fd4-93f6-1c39c7a7544e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLinesOfCredit_019e474a-bfe2-7f34-b443-5cd5a6b9439e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RepaymentsOfLinesOfCredit"/>
    <link:calculationArc order="3" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019e474a-bfe2-7df4-a596-02f193aadbf3" xlink:to="loc_us-gaap_RepaymentsOfLinesOfCredit_019e474a-bfe2-7f34-b443-5cd5a6b9439e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfNotesPayable_019e474a-bfe2-7744-b97e-8c066b1ab02e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RepaymentsOfNotesPayable"/>
    <link:calculationArc order="4" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019e474a-bfe2-7df4-a596-02f193aadbf3" xlink:to="loc_us-gaap_RepaymentsOfNotesPayable_019e474a-bfe2-7744-b97e-8c066b1ab02e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfFinancingCosts_019e474a-bfe2-743b-982c-26d98b23f186" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsOfFinancingCosts"/>
    <link:calculationArc order="5" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019e474a-bfe2-7df4-a596-02f193aadbf3" xlink:to="loc_us-gaap_PaymentsOfFinancingCosts_019e474a-bfe2-743b-982c-26d98b23f186" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfDividendsCommonStock_019e474a-bfe2-7c17-8238-1672e881faff" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsOfDividendsCommonStock"/>
    <link:calculationArc order="6" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019e474a-bfe2-7df4-a596-02f193aadbf3" xlink:to="loc_us-gaap_PaymentsOfDividendsCommonStock_019e474a-bfe2-7c17-8238-1672e881faff" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.gladstoneinvestment.com/role/CONSOLIDATEDSCHEDULEOFINVESTMENTS" xlink:type="simple" xlink:href="gain-20260630.xsd#CONSOLIDATEDSCHEDULEOFINVESTMENTS"/>
  <link:calculationLink xlink:role="http://www.gladstoneinvestment.com/role/CONSOLIDATEDSCHEDULEOFINVESTMENTS" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_gain_InvestmentOwnedAtCostAndMoneyMarketFundsAtCarryingValue_019eabd0-01e6-7c5d-bdb2-ccf08acc4596" xlink:href="gain-20260630.xsd#gain_InvestmentOwnedAtCostAndMoneyMarketFundsAtCarryingValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentOwnedAtCost_019eabd0-01e6-7dae-94bc-9c65be62003a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentOwnedAtCost"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_gain_InvestmentOwnedAtCostAndMoneyMarketFundsAtCarryingValue_019eabd0-01e6-7c5d-bdb2-ccf08acc4596" xlink:to="loc_us-gaap_InvestmentOwnedAtCost_019eabd0-01e6-7dae-94bc-9c65be62003a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MoneyMarketFundsAtCarryingValue_019eabd0-01e6-7735-9449-971df003c37f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MoneyMarketFundsAtCarryingValue"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_gain_InvestmentOwnedAtCostAndMoneyMarketFundsAtCarryingValue_019eabd0-01e6-7c5d-bdb2-ccf08acc4596" xlink:to="loc_us-gaap_MoneyMarketFundsAtCarryingValue_019eabd0-01e6-7735-9449-971df003c37f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gain_InvestmentOwnedAndMoneyMarketFundsAtFairValue_019eabd0-01e6-763e-a41c-605f50716fd3" xlink:href="gain-20260630.xsd#gain_InvestmentOwnedAndMoneyMarketFundsAtFairValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentOwnedAtFairValue_019eabd0-01e6-7446-8e3d-c9330818e210" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentOwnedAtFairValue"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_gain_InvestmentOwnedAndMoneyMarketFundsAtFairValue_019eabd0-01e6-763e-a41c-605f50716fd3" xlink:to="loc_us-gaap_InvestmentOwnedAtFairValue_019eabd0-01e6-7446-8e3d-c9330818e210" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gain_MoneyMarketFundsFairValueDisclosure_019eabd0-01e6-71ce-b2a0-83aab9827106" xlink:href="gain-20260630.xsd#gain_MoneyMarketFundsFairValueDisclosure"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_gain_InvestmentOwnedAndMoneyMarketFundsAtFairValue_019eabd0-01e6-763e-a41c-605f50716fd3" xlink:to="loc_gain_MoneyMarketFundsFairValueDisclosure_019eabd0-01e6-71ce-b2a0-83aab9827106" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.gladstoneinvestment.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESScheduleofCashCashEquivalentsandRestrictedCashDetails" xlink:type="simple" xlink:href="gain-20260630.xsd#SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESScheduleofCashCashEquivalentsandRestrictedCashDetails"/>
  <link:calculationLink xlink:role="http://www.gladstoneinvestment.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESScheduleofCashCashEquivalentsandRestrictedCashDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019e474a-bfe2-7cbe-b080-616d185652e9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Cash_019e474a-bfe2-7064-9b13-488f896735e0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Cash"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019e474a-bfe2-7cbe-b080-616d185652e9" xlink:to="loc_us-gaap_Cash_019e474a-bfe2-7064-9b13-488f896735e0" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MoneyMarketFundsAtCarryingValue_019e474a-bfe2-777b-9888-052ef53f28fa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MoneyMarketFundsAtCarryingValue"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019e474a-bfe2-7cbe-b080-616d185652e9" xlink:to="loc_us-gaap_MoneyMarketFundsAtCarryingValue_019e474a-bfe2-777b-9888-052ef53f28fa" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCash_019e474a-bfe2-742b-834a-3d504436dc26" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedCash"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019e474a-bfe2-7cbe-b080-616d185652e9" xlink:to="loc_us-gaap_RestrictedCash_019e474a-bfe2-742b-834a-3d504436dc26" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.gladstoneinvestment.com/role/INVESTMENTSScheduleofInvestmentPrincipalRepaymentsDetails" xlink:type="simple" xlink:href="gain-20260630.xsd#INVESTMENTSScheduleofInvestmentPrincipalRepaymentsDetails"/>
  <link:calculationLink xlink:role="http://www.gladstoneinvestment.com/role/INVESTMENTSScheduleofInvestmentPrincipalRepaymentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_gain_PrincipalRepaymentAndMaturityOfInvestments_019e474a-c0b2-75b2-8d89-82876cbae940" xlink:href="gain-20260630.xsd#gain_PrincipalRepaymentAndMaturityOfInvestments"/>
    <link:loc xlink:type="locator" xlink:label="loc_gain_PrincipalRepaymentAndMaturityOfInvestmentsRemainderOfFiscalYear_019e474a-c0b2-7aec-a4fe-22abd9491903" xlink:href="gain-20260630.xsd#gain_PrincipalRepaymentAndMaturityOfInvestmentsRemainderOfFiscalYear"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_gain_PrincipalRepaymentAndMaturityOfInvestments_019e474a-c0b2-75b2-8d89-82876cbae940" xlink:to="loc_gain_PrincipalRepaymentAndMaturityOfInvestmentsRemainderOfFiscalYear_019e474a-c0b2-7aec-a4fe-22abd9491903" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gain_PrincipalRepaymentAndMaturityOfInvestmentsYearTwo_019e474a-c0b2-7069-96da-c1ffd5759676" xlink:href="gain-20260630.xsd#gain_PrincipalRepaymentAndMaturityOfInvestmentsYearTwo"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_gain_PrincipalRepaymentAndMaturityOfInvestments_019e474a-c0b2-75b2-8d89-82876cbae940" xlink:to="loc_gain_PrincipalRepaymentAndMaturityOfInvestmentsYearTwo_019e474a-c0b2-7069-96da-c1ffd5759676" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gain_PrincipalRepaymentAndMaturityOfInvestmentsYearOne_019e474a-c0b2-7782-a496-8454f69bc2c0" xlink:href="gain-20260630.xsd#gain_PrincipalRepaymentAndMaturityOfInvestmentsYearOne"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_gain_PrincipalRepaymentAndMaturityOfInvestments_019e474a-c0b2-75b2-8d89-82876cbae940" xlink:to="loc_gain_PrincipalRepaymentAndMaturityOfInvestmentsYearOne_019e474a-c0b2-7782-a496-8454f69bc2c0" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gain_PrincipalRepaymentAndMaturityOfInvestmentsAfterYearFour_019e474a-c0b2-70f8-bb2a-442d014b3094" xlink:href="gain-20260630.xsd#gain_PrincipalRepaymentAndMaturityOfInvestmentsAfterYearFour"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_gain_PrincipalRepaymentAndMaturityOfInvestments_019e474a-c0b2-75b2-8d89-82876cbae940" xlink:to="loc_gain_PrincipalRepaymentAndMaturityOfInvestmentsAfterYearFour_019e474a-c0b2-70f8-bb2a-442d014b3094" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gain_PrincipalRepaymentAndMaturityOfInvestmentsYearFour_019e474a-c0b2-7e6d-bfea-f686b6a24872" xlink:href="gain-20260630.xsd#gain_PrincipalRepaymentAndMaturityOfInvestmentsYearFour"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_gain_PrincipalRepaymentAndMaturityOfInvestments_019e474a-c0b2-75b2-8d89-82876cbae940" xlink:to="loc_gain_PrincipalRepaymentAndMaturityOfInvestmentsYearFour_019e474a-c0b2-7e6d-bfea-f686b6a24872" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gain_PrincipalRepaymentAndMaturityOfInvestmentsYearThree_019e474a-c0b2-7551-a542-27452ae8a49d" xlink:href="gain-20260630.xsd#gain_PrincipalRepaymentAndMaturityOfInvestmentsYearThree"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_gain_PrincipalRepaymentAndMaturityOfInvestments_019e474a-c0b2-75b2-8d89-82876cbae940" xlink:to="loc_gain_PrincipalRepaymentAndMaturityOfInvestmentsYearThree_019e474a-c0b2-7551-a542-27452ae8a49d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentOwnedAtCost_019e474a-c0b2-72d6-8d58-76eb3f83168d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentOwnedAtCost"/>
    <link:loc xlink:type="locator" xlink:label="loc_gain_PrincipalRepaymentAndMaturityOfInvestments_019e474a-c0b2-70f4-bb4e-d0db4286c4f3" xlink:href="gain-20260630.xsd#gain_PrincipalRepaymentAndMaturityOfInvestments"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentOwnedAtCost_019e474a-c0b2-72d6-8d58-76eb3f83168d" xlink:to="loc_gain_PrincipalRepaymentAndMaturityOfInvestments_019e474a-c0b2-70f4-bb4e-d0db4286c4f3" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesFvNiCost_019e474a-c0b2-7980-92e3-0a87fbb70eb2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquitySecuritiesFvNiCost"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentOwnedAtCost_019e474a-c0b2-72d6-8d58-76eb3f83168d" xlink:to="loc_us-gaap_EquitySecuritiesFvNiCost_019e474a-c0b2-7980-92e3-0a87fbb70eb2" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.gladstoneinvestment.com/role/RELATEDPARTYTRANSACTIONSScheduleofRelatedPartyTransactionsDetails" xlink:type="simple" xlink:href="gain-20260630.xsd#RELATEDPARTYTRANSACTIONSScheduleofRelatedPartyTransactionsDetails"/>
  <link:calculationLink xlink:role="http://www.gladstoneinvestment.com/role/RELATEDPARTYTRANSACTIONSScheduleofRelatedPartyTransactionsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_gain_IncentiveFee_019e474a-c0b2-7810-ac2d-efa75b826fda" xlink:href="gain-20260630.xsd#gain_IncentiveFee"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncentiveFeeExpenseIncomeBased_019e474a-c0b2-7738-ae5c-5dcf25696cfb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncentiveFeeExpenseIncomeBased"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_gain_IncentiveFee_019e474a-c0b2-7810-ac2d-efa75b826fda" xlink:to="loc_us-gaap_IncentiveFeeExpenseIncomeBased_019e474a-c0b2-7738-ae5c-5dcf25696cfb" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gain_IncentiveFeeExpenseCapitalGainsBasedNet_019e474a-c0b2-78d2-98a0-45b1ba501e6d" xlink:href="gain-20260630.xsd#gain_IncentiveFeeExpenseCapitalGainsBasedNet"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_gain_IncentiveFee_019e474a-c0b2-7810-ac2d-efa75b826fda" xlink:to="loc_gain_IncentiveFeeExpenseCapitalGainsBasedNet_019e474a-c0b2-78d2-98a0-45b1ba501e6d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gain_NetBaseManagementFee_019e474a-c0b2-7050-a9a1-59f71aaab92e" xlink:href="gain-20260630.xsd#gain_NetBaseManagementFee"/>
    <link:loc xlink:type="locator" xlink:label="loc_gain_InvestmentCompanyCreditsToFeesFromAdviserOther_019e474a-c0b2-7dc2-8512-2c5bff53775d" xlink:href="gain-20260630.xsd#gain_InvestmentCompanyCreditsToFeesFromAdviserOther"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_gain_NetBaseManagementFee_019e474a-c0b2-7050-a9a1-59f71aaab92e" xlink:to="loc_gain_InvestmentCompanyCreditsToFeesFromAdviserOther_019e474a-c0b2-7dc2-8512-2c5bff53775d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ManagementFeeExpense_019e474a-c0b2-7140-9b44-459df940408b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ManagementFeeExpense"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_gain_NetBaseManagementFee_019e474a-c0b2-7050-a9a1-59f71aaab92e" xlink:to="loc_us-gaap_ManagementFeeExpense_019e474a-c0b2-7140-9b44-459df940408b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gain_NetTotalIncentiveFee_019e474a-c0b2-708f-b455-a20185d09816" xlink:href="gain-20260630.xsd#gain_NetTotalIncentiveFee"/>
    <link:loc xlink:type="locator" xlink:label="loc_gain_IncentiveFee_019e474a-c0b2-7df8-8b71-2fd7e6ff0ba3" xlink:href="gain-20260630.xsd#gain_IncentiveFee"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_gain_NetTotalIncentiveFee_019e474a-c0b2-708f-b455-a20185d09816" xlink:to="loc_gain_IncentiveFee_019e474a-c0b2-7df8-8b71-2fd7e6ff0ba3" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gain_InvestmentCompanyCreditsToIncentiveFeesFromAdviserOther_019e474a-c0b2-787e-9910-0b5a53f4be05" xlink:href="gain-20260630.xsd#gain_InvestmentCompanyCreditsToIncentiveFeesFromAdviserOther"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_gain_NetTotalIncentiveFee_019e474a-c0b2-708f-b455-a20185d09816" xlink:to="loc_gain_InvestmentCompanyCreditsToIncentiveFeesFromAdviserOther_019e474a-c0b2-787e-9910-0b5a53f4be05" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gain_NetLoanServicingFee_019e474a-c0b2-7007-b801-c62a142601d7" xlink:href="gain-20260630.xsd#gain_NetLoanServicingFee"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoanProcessingFee_019e474a-c0b2-7d2a-ae9f-e92195df4257" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LoanProcessingFee"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_gain_NetLoanServicingFee_019e474a-c0b2-7007-b801-c62a142601d7" xlink:to="loc_us-gaap_LoanProcessingFee_019e474a-c0b2-7d2a-ae9f-e92195df4257" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gain_InvestmentCompanyCreditsToBaseManagementFeeLoanServicingFee_019e474a-c0b2-7c7f-b2f1-e1b226d92005" xlink:href="gain-20260630.xsd#gain_InvestmentCompanyCreditsToBaseManagementFeeLoanServicingFee"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_gain_NetLoanServicingFee_019e474a-c0b2-7007-b801-c62a142601d7" xlink:to="loc_gain_InvestmentCompanyCreditsToBaseManagementFeeLoanServicingFee_019e474a-c0b2-7c7f-b2f1-e1b226d92005" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.gladstoneinvestment.com/role/BORROWINGSScheduleofDebtDetails" xlink:type="simple" xlink:href="gain-20260630.xsd#BORROWINGSScheduleofDebtDetails"/>
  <link:calculationLink xlink:role="http://www.gladstoneinvestment.com/role/BORROWINGSScheduleofDebtDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_019e474a-c0b2-70e3-8d8e-662283cf56d2" 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_019e474a-c0b2-79aa-b589-06f7c21dc734" 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="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LongTermDebt_019e474a-c0b2-70e3-8d8e-662283cf56d2" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_019e474a-c0b2-79aa-b589-06f7c21dc734" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsGross_019e474a-c0b2-782b-b003-961b5f6aef97" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredFinanceCostsGross"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LongTermDebt_019e474a-c0b2-70e3-8d8e-662283cf56d2" xlink:to="loc_us-gaap_DeferredFinanceCostsGross_019e474a-c0b2-782b-b003-961b5f6aef97" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.gladstoneinvestment.com/role/DISTRIBUTIONSTOCOMMONSTOCKHOLDERSScheduleofCashDistributionstoCommonStockholdersDetails" xlink:type="simple" xlink:href="gain-20260630.xsd#DISTRIBUTIONSTOCOMMONSTOCKHOLDERSScheduleofCashDistributionstoCommonStockholdersDetails"/>
  <link:calculationLink xlink:role="http://www.gladstoneinvestment.com/role/DISTRIBUTIONSTOCOMMONSTOCKHOLDERSScheduleofCashDistributionstoCommonStockholdersDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockDividendsPerShareCashPaid_019e474a-c0b3-7879-ae0d-67892bc1938b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockDividendsPerShareCashPaid"/>
    <link:loc xlink:type="locator" xlink:label="loc_gain_CommonStockDividendsPerSharePaidSupplemental_019e474a-c0b3-7823-8185-e157f16e0479" xlink:href="gain-20260630.xsd#gain_CommonStockDividendsPerSharePaidSupplemental"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CommonStockDividendsPerShareCashPaid_019e474a-c0b3-7879-ae0d-67892bc1938b" xlink:to="loc_gain_CommonStockDividendsPerSharePaidSupplemental_019e474a-c0b3-7823-8185-e157f16e0479" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gain_CommonStockDividendsPerSharePaidOrdinary_019e474a-c0b3-74e7-9555-2ef4cf4b6c64" xlink:href="gain-20260630.xsd#gain_CommonStockDividendsPerSharePaidOrdinary"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CommonStockDividendsPerShareCashPaid_019e474a-c0b3-7879-ae0d-67892bc1938b" xlink:to="loc_gain_CommonStockDividendsPerSharePaidOrdinary_019e474a-c0b3-74e7-9555-2ef4cf4b6c64" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.gladstoneinvestment.com/role/FINANCIALHIGHLIGHTSDetails" xlink:type="simple" xlink:href="gain-20260630.xsd#FINANCIALHIGHLIGHTSDetails"/>
  <link:calculationLink xlink:role="http://www.gladstoneinvestment.com/role/FINANCIALHIGHLIGHTSDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShare_019e474a-c0b3-71b1-aec3-e13e30fd7d3a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShare"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyInvestmentIncomeLossPerShare_019e474a-c0b3-7849-b2b1-ee10c184080d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentCompanyInvestmentIncomeLossPerShare"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShare_019e474a-c0b3-71b1-aec3-e13e30fd7d3a" xlink:to="loc_us-gaap_InvestmentCompanyInvestmentIncomeLossPerShare_019e474a-c0b3-7849-b2b1-ee10c184080d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyRealizedGainLossOnInvestmentPerShare_019e474a-c0b3-7abb-8adf-b58ef0aa73cc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentCompanyRealizedGainLossOnInvestmentPerShare"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShare_019e474a-c0b3-71b1-aec3-e13e30fd7d3a" xlink:to="loc_us-gaap_InvestmentCompanyRealizedGainLossOnInvestmentPerShare_019e474a-c0b3-7abb-8adf-b58ef0aa73cc" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyUnrealizedGainLossOnInvestmentPerShare_019e474a-c0b3-7f9e-9cf3-a9a50f6b6e2d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentCompanyUnrealizedGainLossOnInvestmentPerShare"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShare_019e474a-c0b3-71b1-aec3-e13e30fd7d3a" xlink:to="loc_us-gaap_InvestmentCompanyUnrealizedGainLossOnInvestmentPerShare_019e474a-c0b3-7f9e-9cf3-a9a50f6b6e2d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyDistributionToShareholdersPerShare_019e474a-c0b3-77ae-981d-3f418b6a0b6f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentCompanyDistributionToShareholdersPerShare"/>
    <link:loc xlink:type="locator" xlink:label="loc_gain_InvestmentCompanyDistributionToShareholdersFromNetInvestmentIncomePerShare_019e474a-c0b3-73d2-869b-6f0196381a20" xlink:href="gain-20260630.xsd#gain_InvestmentCompanyDistributionToShareholdersFromNetInvestmentIncomePerShare"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentCompanyDistributionToShareholdersPerShare_019e474a-c0b3-77ae-981d-3f418b6a0b6f" xlink:to="loc_gain_InvestmentCompanyDistributionToShareholdersFromNetInvestmentIncomePerShare_019e474a-c0b3-73d2-869b-6f0196381a20" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gain_InvestmentCompanyDistributionToShareholdersFromNetRealizedGainsPerShare_019e474a-c0b3-7164-8a53-dfb19746435a" xlink:href="gain-20260630.xsd#gain_InvestmentCompanyDistributionToShareholdersFromNetRealizedGainsPerShare"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentCompanyDistributionToShareholdersPerShare_019e474a-c0b3-77ae-981d-3f418b6a0b6f" xlink:to="loc_gain_InvestmentCompanyDistributionToShareholdersFromNetRealizedGainsPerShare_019e474a-c0b3-7164-8a53-dfb19746435a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_gain_InvestmentCompanyNetAccretiveEffectiveOfEquityOffering_019e474a-c0b3-740b-86b2-c1d87e43e317" xlink:href="gain-20260630.xsd#gain_InvestmentCompanyNetAccretiveEffectiveOfEquityOffering"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InvestmentCompanyDistributionToShareholdersPerShare_019e474a-c0b3-77ae-981d-3f418b6a0b6f" xlink:to="loc_gain_InvestmentCompanyNetAccretiveEffectiveOfEquityOffering_019e474a-c0b3-740b-86b2-c1d87e43e317" xlink:type="arc"/>
  </link:calculationLink>
</link:linkbase>
