How do you measure for a filter to fit your monitor?

Answer 1

Filters (if they sell them anymore) are sold by monitor sizes, usually in inches.

If you know your monitor size (ie: 17", 19", etc) then it's a simple matter of choosing a filter that is suitable for that size. If you don't know the size of your monitor, check on the sticker on the back of the monitor and you'll find the size in the description. Otherwise, take a tape measure and measure the screen size diagonally (ie: top left to bottom right corners) in inches, and you can safely assume the nearest value to be the monitor size.

Answer 2

Measure the screen diagonally top R/hand corner to bottom L/hand corner