Ok so Monitors come in annoying Merkin Imperial sizes, and the size is measured across the Diagonal. Neither of which help me when I am trying to determine in Metric how wide a monitor is.
So I created a quick Excel spreadsheet that lets you check the size in Inches then determine the Width and Height in either Inches/MM. (Only the screen, this obviously can't determine the size of the bezel around the screen)
I have it in 16x10(which most widescreen PC monitors are) 16x9(widescreen TVs) and 4x3(Non-Widescreen format common to TVs and Monitors).
I have used 30,27,24,22,19 inch sizes, as they fit most common sizes around nowadays.
So when you look at the spreadsheet, you will see that a 24" 16x10 PC monitor will have a Height of 12.72"/323.09mm and a width of 20.35"/516.94mm