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<xbrl
  xmlns="http://www.xbrl.org/2003/instance"
  xmlns:dei="http://xbrl.sec.gov/dei/2026"
  xmlns:ffd="http://xbrl.sec.gov/ffd/2026"
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    <link:schemaRef
      xlink:href="https://xbrl.sec.gov/ffd/2026/ffd-2026.xsd"
      xlink:type="simple"/>
    <context id="rc">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0001476765</identifier>
        </entity>
        <period>
            <startDate>2026-05-20</startDate>
            <endDate>2026-05-20</endDate>
        </period>
    </context>
    <context id="offrl_1">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0001476765</identifier>
            <segment>
                <xbrldi:typedMember dimension="ffd:OfferingAxis">
                    <dei:lineNo>1</dei:lineNo>
                </xbrldi:typedMember>
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        </entity>
        <period>
            <startDate>2026-05-20</startDate>
            <endDate>2026-05-20</endDate>
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    </context>
    <unit id="USD">
        <measure>iso4217:USD</measure>
    </unit>
    <unit id="pure">
        <measure>pure</measure>
    </unit>
    <unit id="Shares">
        <measure>shares</measure>
    </unit>
    <ffd:FormTp contextRef="rc" id="ixv-344">N-2</ffd:FormTp>
    <ffd:SubmissnTp contextRef="rc" id="ixv-345">424B2</ffd:SubmissnTp>
    <ffd:FeeExhibitTp contextRef="rc" id="ixv-346">EX-FILING FEES</ffd:FeeExhibitTp>
    <ffd:RegnFileNb contextRef="rc" id="ixv-347">333-286240</ffd:RegnFileNb>
    <dei:EntityCentralIndexKey contextRef="rc" id="ixv-348">0001476765</dei:EntityCentralIndexKey>
    <dei:EntityRegistrantName contextRef="rc" id="ixv-349">GOLUB CAPITAL BDC, Inc.</dei:EntityRegistrantName>
    <ffd:OfferingTableNa contextRef="rc" id="hiddenrcOfferingTableNa" xsi:nil="true"/>
    <ffd:OffsetTableNa contextRef="rc" id="hiddenrcOffsetTableNa">N/A</ffd:OffsetTableNa>
    <ffd:CombinedProspectusTableNa contextRef="rc" id="hiddenrcCombinedProspectusTableNa">N/A</ffd:CombinedProspectusTableNa>
    <ffd:FormTp contextRef="rc" id="ixv-377">N-2</ffd:FormTp>
    <dei:EntityRegistrantName contextRef="rc" id="ixv-378">GOLUB CAPITAL BDC, Inc.</dei:EntityRegistrantName>
    <ffd:PrevslyPdFlg contextRef="offrl_1" id="ixv-379">false</ffd:PrevslyPdFlg>
    <ffd:OfferingSctyTp contextRef="offrl_1" id="ixv-380">Debt</ffd:OfferingSctyTp>
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    <ffd:AmtSctiesRegd
      contextRef="offrl_1"
      decimals="0"
      id="ixv-383"
      unitRef="Shares">500000000</ffd:AmtSctiesRegd>
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      contextRef="offrl_1"
      decimals="2"
      id="ixv-384"
      unitRef="USD">494555000.00</ffd:MaxAggtOfferingPric>
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      contextRef="offrl_1"
      decimals="7"
      id="ixv-385"
      unitRef="pure">0.0001381</ffd:FeeRate>
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      contextRef="offrl_1"
      decimals="2"
      id="ixv-386"
      unitRef="USD">68298.05</ffd:FeeAmt>
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    <ffd:TtlPrevslyPdAmt contextRef="rc" decimals="2" id="ixv-389" unitRef="USD">0.00</ffd:TtlPrevslyPdAmt>
    <ffd:TtlOffsetAmt contextRef="rc" decimals="2" id="ixv-390" unitRef="USD">0.00</ffd:TtlOffsetAmt>
    <ffd:NetFeeAmt contextRef="rc" decimals="2" id="ixv-391" unitRef="USD">68298.05</ffd:NetFeeAmt>
    <ffd:OfferingNote contextRef="offrl_1" id="ixv-392">The registration fee is calculated in accordance with Rule 457(o) under the Securities Act of 1933, as amended (the "Securities Act"), based on the proposed maximum aggregate offering price, and Rule 456(b) and 457(r) under the Securities Act. In accordance with Rules 456(b) and 457(r) under the Securities Act, Golub Capital BDC, Inc. (the "Registrant") initially deferred payment of all of the registration fees relating to the Registrant's Registration Statement on Form N-2 (File No. 333-286240), which was filed with the Securities and Exchange Commission (the "SEC") on March 28, 2025 and automatically became effective upon filing with the SEC (the "Registration Statement"). This "Calculation of Filing Fee Table" shall be deemed to update the "Calculation of Filing Fee Table" in the Registration Statement. </ffd:OfferingNote>
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    <ffd:FnlPrspctsFlg contextRef="rc" id="ixv-394">true</ffd:FnlPrspctsFlg>
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