If you want to know 1024 pixels equal to what millimetres, i think this article will help you.
Step 1: Know how to convert
Usually, i should remember this expression:1pix=0.264583333mm
So,if you want to convert 1024 pixels to mm, you can multiply it by 0.264583333. That is 1024*0.264583333
You see, it is very easy!