Calculate your arrow's kinetic energy (KE) in ft-lbs and Joules. Optimize your hunting setup for ethical shots and maximum impact power.
Enter the total arrow weight in grains and the speed of the arrow in feet per second (fps) measured through a chronograph.
Kinetic Energy (KE) is the total energy available to crush bone, while Momentum (M) is the ability of the arrow to keep moving through the target.
Serious hunters focus on momentum for heavy game (like elk or moose) to ensure a complete pass-through, which provides better tracking and faster kills.
Kinetic energy (KE) is calculated using the formula: KE = (Weight in grains × Velocity² / 450,240). Our tool automates this to help you meet minimum hunting requirements. For example, a 420-grain arrow at 290 fps gives 420 × 290² ÷ 450,240 ≈ 78.4 ft-lbf. To convert to joules, multiply the foot-pound figure by 1.35582, so that same arrow carries about 106 J.
Most experts recommend at least 25-30 ft-lbs of KE for small game and 40-50 ft-lbs for whitetail deer to ensure an ethical and effective harvest. This calculator labels results by quarry class: under 25 ft-lbf is small game, 25 to 40 is small-to-medium, 40 to 65 is deer-sized game, 65 to 100 is elk and other large animals, and 100 or more is the dangerous-game range used for cape buffalo and similar.
Because KE depends on velocity squared but only the first power of mass, speed has an outsized effect. Adding 10% to your arrow's speed raises kinetic energy by about 21%, while adding 10% to weight raises it by only 10%. This is the opposite of momentum, which is linear in both — and it is why heavy-arrow advocates favor momentum for penetration even though a light, fast arrow may show higher KE.