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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2020-07-01</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001433195</issuerCik>
        <issuerName>APPFOLIO INC</issuerName>
        <issuerTradingSymbol>APPF</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001645481</rptOwnerCik>
            <rptOwnerName>IGSB IVP III, LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O IGSB, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>1485 E. VALLEY ROAD, SUITE H</rptOwnerStreet2>
            <rptOwnerCity>SANTA BARBARA</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>93108</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Class B Common Stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>0.00</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2020-07-01</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>300691</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.00</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F2"/>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F2"/>
                <footnoteId id="F3"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Class A Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>300691</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>3554584</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">On July 1, 2020, the investors in one of the investment funds of IGSB IVP III, LLC (&quot;IVP III&quot;) approved the termination of that investment fund and the distribution of all 300,691 shares of AppFolio Class B Common Stock (&quot;Class B Shares&quot;) held by that fund, pro-rata to the investors in that fund.  No consideration was paid by any of those investors for the respective Class B Shares distributed to them.</footnote>
        <footnote id="F2">Each Class B Share is convertible, at any time at the option of the holder, into one Class A Share.  In addition, Class B Shares that are sold or otherwise transferred will convert automatically, on a one share-for-one share basis, into Class A Shares, except for (i) any transfer by a partnership or limited liability company that was a registered holder of Class B Shares prior to June 30, 2015 that is made to anyone who was a partner or member of any such partnership or limited liability company prior to June 30, 2015, and (ii) any transfer to a &quot;qualified recipient&quot; (as defined in AppFolio's Amended and Restated Certificate of Incorporation).</footnote>
        <footnote id="F3">(Continued from footnote 2)  AppFolio's Class B Shares do not have an expiration date.  However, all of the outstanding Class B Shares will convert automatically into Class A Shares, on a one share-for-one share basis, on the date when the number of the Company's outstanding Class B Shares represents less than 10% of the sum of AppFolio's outstanding Class A and Class B Shares.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>IGSB IVP III, LLC, a California limited liability company, By: Investment Group of Santa Barbara, LLC, a California limited liability company, By: Timothy K. Bliss, Member &amp; Vice President, By: /s/ Kimberly Shea, Attorney-in-Fact for Timothy K. Bliss</signatureName>
        <signatureDate>2020-07-06</signatureDate>
    </ownerSignature>
</ownershipDocument>
