[8D] i can help you with this i know it. you need to weight you're arrows with you're feild tip or broadhead on it. then you need get a cronograh and see how fast the bow shoots the arrow. then you call a good bow shop and ask for the formula for kinetic energy. just be sure to writ this formula dow and keep it in a safe place. i do this with my arrows all the time. but you need to know the speed/weight of the arrow. good luck