This is a little program I wrote for calculating FOV, based partially on a code from rjdown's BFBC2 FOV Calculator http://www.rjdown.co.uk/projects/bfbc2/fovcalculator.php.
It pretty much does the same thing, except it doesn't round numbers too much. Nothing more nothing less. If you find the messy code satisfactory , you feel free to implement it into your own FOV Changers.