Pixel to MM equation?

Question

Is there a reliable equation to work out pixel size to MM? Or is that not possible cross device?

We are working with a bespoke system that delivers content to many devices with different screen sizes, it can detect the screen width in MM, but we would like to accurately convert this to pixel size to deliver correctly sized images dynamically using a simple jquery script!?

Any ideas?

Cheers Paul

Answer 1

What i did :

 <div id="my_mm" style="height:100mm;display:none"></div>

Then:

var pxTomm = function(px){   
   return Math.floor(px/($('#my_mm').height()/100)); //JQuery returns sizes in PX
 };