Arrow Kinetic Energy & Momentum
Energy and momentum from arrow weight and speed.
How this works
Momentum (lb·s) = arrow weight (gr) × speed (fps) ÷ 225,218
These are the same physics formulas used for firearms bullets (see the Muzzle/Downrange Energy calculator), just applied to arrow weight and speed instead. Because arrows are far slower and heavier relative to their speed than bullets, momentum plays a proportionally bigger role in how well an arrow penetrates.
Energy for the label, momentum for the penetration
Kinetic energy is the number most often quoted in minimum-energy guidelines for bowhunting big game, but many bowhunters also watch momentum closely since it tracks more directly with how deeply and reliably a fixed-blade or mechanical broadhead drives through bone and tissue. A heavier, slightly slower arrow often out-penetrates a lighter, faster one with the same kinetic energy.
Frequently asked questions
Which number matters more for hunting — energy or momentum?
Both are commonly cited, but many bowhunting educators point to momentum as tracking actual penetration more closely, while energy is the figure most often quoted in minimum-energy guidelines by game size.
Can two arrows have the same energy but different momentum?
Yes — since energy scales with speed squared and momentum scales with speed directly, a lighter, faster arrow and a heavier, slower one can match on energy while differing meaningfully on momentum.
What's a reasonable kinetic energy target for deer-sized game?
Many hunting educators cite roughly 25 ft-lb as a commonly referenced rule-of-thumb minimum for deer-sized game, with larger animals often suggested at 40+ ft-lb — check guidance specific to your target species.
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