Converting width from percentage to pixels

Answer 1

This happens when you use percent + padding. Pixel is int and so it will be rounded.

In your example: 10%, 20% and 70% is the width of the container and than you need to add the padding and border.

With this decimal numbers will occur and than need to be rounded.

EXAMPLE:

Your page is 900px width. Without padding, margin or border you will have widths of 630px (70%), 160px (20%), 90px (10%).

But when you add the border + padding the percents must be calculated from 900 - (3 tds * 10px padding (left and right)) - (3 tds * 2px border(left and right)) = 864px.

With 864px width you will get: 604,8px (70%), 172,8px (20%), 86,4px (10%).

And this is where the 1px difference occures.

Answer 2

<div id="div-1" style="width: 1000px;">
    <div id="div-2" style="width: 10%;"></div>
</div>

<script language="javascript">                
    var percents = parseInt(document.getElementById("div-2").style.width);
    var parentWidth = parseInt(document.getElementById("div-1").style.width);
    var pixels = parentWidth*(percents/100);
    alert(pixels); // will print "100"
</script>

Answer 3

Try using .outerWidth() instead of .width()