1$(function() {
2  $("#subtotal").html(sumColumn(4));
3  $("#total").html(sumColumn(5));
4});
5
6function sumColumn(index) {
7  var total = 0;
8  $("td:nth-child(" + index + ")").each(function() {
9    total += parseInt($(this).text(), 10) || 0;
10  });  
11  return total;
12}
13<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
14<table style="border-spacing: 10px;">
15  <tr>
16    <td>ClientName</td>
17    <td>ItemName</td>
18    <td>Quantity</td>
19    <td>12</td>
20    <td>34</td>
21  </tr>
22  <tr>
23    <td>ClientName</td>
24    <td>ItemName</td>
25    <td>Quantity</td>
26    <td>56</td>
27    <td>78</td>
28  </tr>
29  <tr>
30    <td>ClientName</td>
31    <td>ItemName</td>
32    <td>Quantity</td>
33    <td>90</td>
34    <td>12</td>
35  </tr>
36  <tr>
37    <td colspan="3">Totals</td>
38    <td id="subtotal"></td>
39    <td id="total"></td>
40  </tr>
41</table>