Crossbow Kinetic Energy: The Chart, the Formula, and How Much a Deer Needs

Deer & Deer Hunting states the calculation as: multiply the arrow speed by itself, multiply that total by the arrow weight, then divide by 450,800. The constant is what converts grains and feet per second into foot-pounds.

Their worked example is the single most useful thing on this page, because it breaks the intuition that faster means harder-hitting:

The heavier arrow gives up 30 FPS and gains 7 ft-lb. That is the whole argument for arrow weight in one table: energy scales with the square of speed, but you do not get to choose speed freely — your bow does, and adding arrow weight is what takes speed away. Adding 75 grains cost 30 FPS and still came out ahead.

Every figure below is the formula applied to the two inputs in the row and column — no estimates, no product claims. Find your bow’s advertised speed on the left and your finished arrow weight across the top.

Two things to read off it. First, the whole tableis above every published game-class minimum, including elk. Second, moving one column to the right — 50 grains of arrow weight — buys about the same energy as moving 25 to 50 FPS up the rows, and the arrow costs a fraction of the bow.

One honest caveat: advertised speed is measured with the maker’s own arrow. Add weight and you lose speed, so the right-hand columns overstate what you will actually clock. Use the table to understand the shape of the trade, then chronograph your real setup if you want your exact number.

You will also see a 100 ft-lb figure quoted for whitetail in crossbow articles. We are not presenting it as a published standard because we have not found it stated by a standards-setting body — but it is worth understanding what it is for. It is a margin figure: it assumes a quartering shot, a shoulder, and a few yards more than you meant to take. Every row in the chart above clears it anyway.

Kinetic energy weights speed twice and weight once. Momentum weights them equally — arrow weight in grains times speed, divided by 225,218, gives momentum in slug-feet per second. That difference is why two setups can tie on energy and behave differently on an animal.

Practically: energy is a reasonable proxy for how much work the arrow can do, and momentum is a better proxy for whether it keeps going after it meets resistance — hide, a rib, a shoulder blade. This is the arithmetic behind the near-universal advice to shoot a heavier arrow for bigger animals even when your energy number already looks fine.

Neither number predicts a pass-through on its own. Broadhead design, arrow straightness and where you hit all matter more than the last 10 ft-lb.

A note on what does not work: lighter arrows. They raise advertised speed and lower delivered energy, and most makers publish a minimum finished arrow weight precisely because going under it is treated as a dry-fire-class risk.

If you want to add weight on purpose rather than by accident, these are the two arrows we point people at. The CenterPunch16 is heavy by design — 410 grains finished, a 92-grain brass insert, about 17 percent FOC — and the Executioner family lets you pick your straightness tolerance and supplies both half-moon and flat nocks in the box.

Check your crossbow’s required nock and minimum arrow length before ordering either one — crossbow arrows are not interchangeable, and the nock is the part the string hits.

Once you know your number, the broadhead is how you spend it. A wide mechanical converts energy into cutting diameter and costs you penetration; a compact fixed head converts it into depth. On a 140 ft-lb bow shooting whitetails, either works. On a lower-energy bow, or on anything bigger than a deer, the fixed head is the safer allocation.