There is a simpler formula, velocity times velocity times bullet weight divided by 450,240.
My old army gives me 1102 fps with a rb, 41 gr of Swiss FFFG so I get 385 foot #. Does a good job on deer I can say.
Yep, there's also a handy-dandy "bullet energy calculator" one can Google. Plug in your weight and speed and Robert's your Uncle!
Mike