The perfect FoV usually is the same as real-world monitor FoV, but some people prefer higher.
Diagonal FoV is higher than horizontal or vertical FoV
(i.e. sitting closer to a bigger monitor -> higher FoV)
You can use a online calculator (e.g.
here) or calculate yourself (see below)
Diagonal FoV:
Code:
2xArcTan[diagonal/(2*view distance)]
Horizontal FoV
Code:
2xArcTan[(diagonal*0.8715)/(2*view distance)]
with Cos[ArcTan[9/16]] ~= 0.8715
Examples:
Sitting 20" away from a 24" monitor has a 55 degree horizontal FoV.
Sitting 80" away from a 55" TV has a 33 degree horizontal FoV.