<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2017-03-07</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001484565</issuerCik>
        <issuerName>Capnia, Inc.</issuerName>
        <issuerTradingSymbol>CAPN</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001120443</rptOwnerCik>
            <rptOwnerName>TP MANAGEMENT VII LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>100 SHORELINE HWY, SUITE 282, BLDG B</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>MILL VALLEY</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94941</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001120461</rptOwnerCik>
            <rptOwnerName>TECHNOLOGY PARTNERS FUND VII LP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>100 SHORELINE HWY, SUITE 282, BLDG B</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>MILL VALLEY</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94941</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001133704</rptOwnerCik>
            <rptOwnerName>TECHNOLOGY PARTNERS AFFILIATES VII LP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>100 SHORELINE HWY, SUITE 282, BLDG B</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>MILL VALLEY</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94941</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2017-03-07</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>77752</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>6904925</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnote</value>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The shares were purchased by the reporting person in a private transaction between the reporting person and a former shareholder of Essentialis in exchange for cash to be used to satisfy certain withholding obligations of the shareholder, based on the closing price per share of Issuer common stock on March 7, 2017 of $0.68.</footnote>
        <footnote id="F2">The shares are held directly by Technology Partners Fund VII, L.P. (&quot;Technology Partners VII&quot;). The Reporting Person is the sole general partner of Technology Partners VII, and may be deemed to beneficially own such shares. The Reporting Person holds voting and dispositive power with respect to the securities held by Technology Partners VII. James Glasheen, Sheila Mutter, Roger Quy, Ira Ehrenpreis, and Ted Ardell, and certain other individuals are members of the Reporting Person and disclaim beneficial ownership of the securities held by Technology Partners VII except to the extent of any pecuniary interest therein.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>James Glasheen, as a Managing Member of TP Management VII, LLC</signatureName>
        <signatureDate>2017-03-09</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>James Glasheen, as a Managing Member of TP Management VII, LLC, the sole general partner of Technology Partners Fund VII, L.P.</signatureName>
        <signatureDate>2017-03-09</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>James Glasheen, as a Managing Member of TP Management VII, LLC, the sole general partner of Technology Partners Affiliates VII, L.P</signatureName>
        <signatureDate>2017-03-09</signatureDate>
    </ownerSignature>
</ownershipDocument>
