Arrow Speed Calculator

This calculator uses an energy model: it estimates how much energy your bow stores from draw weight and draw length, applies a transfer efficiency for the bow type, then converts the arrow’s kinetic energy into speed with v = sqrt(2E/m). It is an estimate, not a measurement — a chronograph always wins for the true number.

Stored energy (ft-lb) = shape factor × draw weight (lb) × draw length (in) / 12. Arrow energy = efficiency × stored energy. Speed (fps) = sqrt(2 × arrow energy / arrow mass in slugs), where arrow mass in slugs = (grains / 7000) / 32.174. The full derivation with every assumption is in the methodology section above.

No. The calculator works from draw weight, draw length, arrow weight and bow type alone — no IBO rating needed. If you do know your bow’s IBO rating, the optional IBO checker compares it against the model’s IBO-condition result (70 lb, 30 in, 350 gr) to show how your setup runs relative to the factory rating.

Treat it as a planning estimate, typically within a few percent of a chronograph for mainstream setups. Real bows vary: string material, cam design, brace height, peep and silencers all shift efficiency, and the model assumes efficiency stays constant. A chronograph measures your actual arrow; no formula can beat that.

The levers, in order of effect: shoot a lighter arrow (never below 5 grains per pound of draw weight), increase draw weight, lengthen your draw, and reduce string weight. Each has trade-offs — lighter arrows carry less momentum and are louder, and heavier draw weight is harder to hold steady. The weight-effect table above shows the exact modelled trade-off for your setup.

In this model, about 0.5 fps per grain around typical hunting setups (roughly 1 fps per 2 grains). In the field the loss is often smaller, because real bows transfer energy more efficiently to heavier arrows while the model holds efficiency constant — so treat the table’s per-grain numbers as an upper bound on speed loss.

Yes. Stored energy scales with peak draw weight, and speed scales with the square root of energy — so doubling draw weight does not double speed. As a rough guide, adding 10 lb of draw weight typically adds on the order of 15–25 fps at common hunting setups, with the exact number depending on draw length, arrow weight and bow type.

Yes. A longer draw stores energy over a longer power stroke, so energy scales linearly with draw length. The common rule of thumb is about 10 fps per inch of draw length, and the model agrees closely with that figure across typical setups.

Two reasons. First, a compound’s cams reshape the draw curve so it stores far more energy at the same peak weight (that is the shape factor in the formula). Second, compounds transfer a higher fraction of that energy to the arrow. A 50 lb recurve and a 50 lb compound are very different machines despite the same number on the limb.

Speed alone is not the criterion — kinetic energy and momentum are. The commonly cited community minimum for deer-size game is about 25 ft-lb of kinetic energy with momentum around 0.40 slug·ft/s, and many hunters prefer 40+ ft-lb for extra margin. This calculator shows both numbers and a readiness band, but they are community guidelines, not law — check your local regulations.

Elk are commonly cited as needing roughly 42–65 ft-lb of kinetic energy with momentum around 0.55 slug·ft/s or more. That usually means a heavier arrow rather than simply a faster one, because momentum — mass times velocity — is what drives penetration. The results panel flags which band your setup falls in.

No. Speed comes at a cost: lighter arrows carry less momentum for penetration, are louder, and magnify tuning problems. They also flirt with the 5-grains-per-pound safety floor. Many experienced bowhunters deliberately trade 10–20 fps for a heavier, quieter, harder-hitting arrow.

It is the minimum safe arrow weight: your arrow must weigh at least 5 grains for every pound of peak draw weight (a 70 lb bow needs a 350+ grain arrow). Lighter is effectively a dry fire and can crack limbs and void warranties. This calculator warns you if your arrow drops below that floor.

No — crossbows are out of scope here. They combine very high draw weights with very short power strokes, so the vertical-bow energy model does not apply. Use a dedicated crossbow speed calculator (or the manufacturer’s chart) instead; several appear in the autocomplete suggestions for this topic.

They live in different regimes. A fast hunting arrow leaves the bow around 280–330 fps carrying roughly 60–90 ft-lb of energy; a rifle bullet travels 2,500–3,000 fps with thousands of ft-lb. Arrows kill by hemorrhage from a cutting broadhead, bullets by hydrostatic shock — which is why archery emphasizes momentum and sharp broadheads over raw speed.

The fastest production compound bows are rated around 350–360 fps under IBO test conditions (70 lb, 30-inch draw, 350-grain arrow), and specialty speed bows push a little beyond that. Crossbows are a separate category and have passed 500 fps. Be skeptical of any vertical-bow claim far above 360 fps without a chronograph video to back it up.