html input get number
<form id="frm1" action="Calculate.html">
<table width="350px" border="1px">
<tr>
<th colspan="2">Availability</th>
</tr>
<tr>
<td>Total Production Time</td>
<td>
<input type="number" id="TotalProductionTime" placeholder="">hours</td>
</tr>
<tr>
<td>Breaks</td>
<td>
<input type="number" id="Breaks" placeholder="">minutes</td>
</tr>
<tr>
<td>Malfunctions</td>
<td>
<input type="number" id="Malfunctions" placeholder="">minutes</td>
</tr>
<tr>
<td>Theoretical production time:</td>
<td>
<p id="test"></p>
</td>
</tr>
</table>
<input type="button" onclick="Calculate()" value="calculate">
</form>
function Calculate() {
var TotalProductionTime = document.getElementById("TotalProductionTime").value;
var TotalProductionTimeInMinutes = TotalProductionTime * 60;
var Breaks = document.getElementById("Breaks").value;
var Malfunctions = document.getElementById("Malfunctions").value;
var TheoreticalProductionTime = TotalProductionTimeInMinutes - Breaks - Malfunctions;
document.getElementById("test").innerHTML = TheoreticalProductionTime;
}