Thanks for the input, but this hasn’t help me find what I’m after.  I don’t need the percentage of the screen an element is taking up, or the size of the screen in pixels but I need the screen size in (millimetre, centimetre, inch etc.), and I wasn’t able to work this out from your answer because it doesn’t help me find how many pixels are in 1 centimetre.

Just What I was looking for, thanks heaps. I will find a way to identify the current device model and hard code the related screen values to pull from. I am only working with Ipad's so found it easier to calculate using PPI.

Just What I was looking for, thanks heaps. I will find a way to identify the current device model and hard code the related screen values to pull from. I am only working with Ipad's so found it easier to calculate using PPI.