JSFiddle - React, Tailwind, and code Playground

HTML

<table width="100%" border="0" cellspacing="0" cellpadding="5">
    <tr>
        <td width="33%">SIZE</td>
        <td width="33%">QUANTITY</td>
        <td width="33%">CUBICS</td>
    </tr>
    <tr>
        <td width="33%">07" E Flute</td>
        <td width="33%">
            <input id="07flute" type="text" value="0" />
        </td>
        <td width="33%"><span id="cubics"></span>

        </td>
    </tr>
    <tr>
        <td width="33%">08" E Flute</td>
        <td width="33%">
            <input id="08flute" type="text" value="0" />
        </td>
        <td width="33%"><span id="cubics2"></span>

        </td>
    </tr>
    <tr>
        <td width="33%">09" E Flute</td>
        <td width="33%">
            <input id="09flute" type="text" value="0" />
        </td>
        <td width="33%"><span id="cubics3"></span>

        </td>
    </tr>
    <tr class="bg">
        <td width="33%">TOTAL</td>
        <td width="33%"><span class="totalquantity"></span>

        </td>
        <td width="33%"><span class="totalcubics"></span>

        </td>
    </tr>
</table>

CSS

.bg {
    background:#c20;
    color:#FFFFFF;
}

JavaScript

function doSum(){
    var one = parseFloat($("#cubics").text(),10);
    if(isNaN(one)) one = 0; 
    var two = parseFloat($("#cubics2").text(),10);
    if(isNaN(two)) two = 0; 
    var three = parseFloat($("#cubics3").text(),10);    
    if(isNaN(three)) three = 0;     
    $('.totalcubics').text(one+two+three); 
}
$("#07flute").keyup(function () {
    var val = parseFloat($(this).val());
    val = (val ? val / 50 * 4.0113 : "Invalid number");
    $("table #cubics").text(val);
    doSum();
});

$("#08flute").keyup(function () {
    var val = parseFloat($(this).val());
    val = (val ? val / 50 * 0.0128 : "Invalid number");
    $("#cubics2").text(val);
    doSum();
});

$("#09flute").keyup(function () {
    var val = parseFloat($(this).val());
    val = (val ? val / 50 * 0.0128 : "Invalid number");
    $("#cubics3").text(val);
    doSum();
});