Arrow Kinetic Energy & Momentum Calculator

Archery uses two standard figures to describe an arrow's downrange performance, both built from total arrow weight in grains (7000 grains = 1 lb) and chronographed speed in feet per second — verified via web search against Easton Archery's and other archery-industry references rather than relied on from memory. Kinetic energy, KE = weight × speed² ÷ 450,240 (ft-lbs), is the arrow's 'power potential' at impact. Momentum, weight × speed ÷ 225,218 (slug-ft/s), doesn't square the speed, so a heavier, slower arrow can carry more momentum than a lighter, faster one with identical kinetic energy — momentum tracks penetration more closely, while kinetic energy tracks raw impact power.

Both divisor constants fold in the grains-to-slugs unit conversion (7000 grains per pound, divided by standard gravity 32.174 ft/s² gives 225,218 for momentum, doubled for kinetic energy's extra factor of speed) so the result comes out directly in the ft-lbs and slug-ft/s units archers actually use, without a separate conversion step.

The result is also compared against a commonly published game-class kinetic-energy guideline (small game under 25 ft-lbs, deer-class medium game 25-41, elk/bear-class large game 42-64, and 65+ for the toughest game) — a practical shot-selection guideline from archery-industry sources, not a strict physical law, so treat it as a starting point rather than a guarantee.