<html>
<head>
<script type="text/javascript">
function mAtoPercentage()
{
document.getElementById("percentage").innerHTML=((18-4)/16)*100;
}
</script>
</head>
<body onload="mAtoPercentage();">
<table>
<tbody>
<td>mA = </td>
<td><form onchange="mAtoPercentage()"><input type="number" name="mA"/></form></td>
<td>mA</td>
</tr>
<tr>
<td><strong>Calculated % = </strong></td>
<td><strong><p id="percentage">__</p></strong></td>
<td><strong>% (4-20mA)</strong></td>
</tr>
</tbody>
</table>
</body>
</html>