How to measure size of my monitor?

Hi!! I am using compaq computer,my monitor is also of compzq,I bought it in 2003.It is big one which occupies much space at the back(not flat) what are these monitors called ,If I am right flat ones are LCDs and LEDs.I want to know how many inches is my computer ? How can i measure with an inch tape ,is it the size of screen only or including the body alos?