Arrow Speed Calculator

Work it out, and see what it means.

Estimated arrow speed290 fps88.392 m/s. This is an EMPIRICAL trade formula, not a derivation — expect a few percent against a chronograph

Draw length adjustment-10 fps10 fps per inch from the 30-inch IBO standard, and the single biggest term in the formula

Arrow weight adjustment-25 fps1 fps lost per 3 grains above the 325 grain minimum

String accessory adjustment-5 fps

Kinetic energy101.2567 J74.6831 ft·lb — the figure hunters quote, and what actually matters for penetration

Momentum2.29108 kg·m/sa heavier, slower arrow carries MORE momentum from the same bow, which is why heavy arrows penetrate better despite being slower

Grains per pound of draw6.1538a normal range, above the 5 gpp safety floor

Time to 20 yards206.897 msignoring drag, which is small over this distance

Why heavier is not simply worseit takes more of the bow's energya light arrow leaves fast but wastes energy in the moving limbs and string. A heavier one absorbs a larger share of the stored energy, so it carries more kinetic energy and far more momentum despite the lower speed

The formula

v ≈ IBO − 10(30 − DL) − (grains − 5×DW)/3 − string/3

An industry rule of thumb

The IBO rating is measured under fixed conditions: a 30-inch draw, 70 pounds and a 350-grain arrow. Real setups differ, and the trade adjusts with a linear formula — ten feet per second per inch of draw length, one foot per second per three grains of arrow weight above the five-grains-per-pound minimum. It is a fit to experience rather than a derivation, and a chronograph will disagree by a few percent.

Heavy arrows are not slower for nothing

A light arrow leaves the bow quickly but leaves much of the stored energy behind in the moving limbs and string. A heavier arrow absorbs a larger share of it, so despite the lower speed it carries more kinetic energy and considerably more momentum — which is why heavy arrows penetrate better.

The five-grains-per-pound floor is a safety limit, not a preference. Below it the bow cannot transfer its energy into the arrow and dumps it into its own limbs instead, which is effectively a dry fire and voids every manufacturer warranty.