Claim of people 

A lot of people claim that 90 degrees horizontal is a good FoV to play with, so if you want to get that, if you have a 16:9 monitor such as 1920x1080 you'd set the vertical FoV to 59, and if you have a 16:10 monitor such as 1680x1050 you'd set it to 64 degrees.

But I included a bunch of others in the table because not everybody likes the same field of view. Some swear by setting it to the maximum, and I also included settings that would get you 90 degrees diagonal and settings that would get you 75 degrees horizontal just to fill the table out.

The higher the FoV, the more you see but the more perspective distortion you get (eg things to your left or right looking stretched). So you may or may not be able to tolerate that. More FOV calculator also makes things in front of you look smaller, obviously, so aiming may be less accurate but only by a small amount. All things to be taken into consideration but it's about finding the balance that works for you.