What Is Foot-Pounds of Energy (FPE)?
Foot-pounds of energy measures the kinetic energy of a moving projectile, commonly used to compare bullet or arrow performance. It’s derived from the classic kinetic energy formula KE = ½mv2, converted into the mixed units of grains and feet-per-second: FPE = (weight in grains × velocity in fps2) ÷ 450,240.
The constant 450,240 accounts for converting grains to pounds-mass and reconciling velocity units, so the result comes out directly in foot-pounds. This value is used for general reference and comparison purposes only.
Last reviewed August 2026