Arrow FOC Calculator

FOC is negative whenever the balance point sits behind the arrow's true geometric midpoint rather than ahead of it, which happens with a very long shaft paired with a balance point that hasn't moved forward to match — for example a long target shaft with a light point and heavy fletching. A negative or near-zero FOC generally signals unstable, tail-heavy flight, and the classification will flag it as too low rather than a data-entry mistake, so it is worth double-checking your balance-point measurement if you see it.

Rest the fully assembled arrow — point, shaft, fletching, and nock all installed — across a single finger or a narrow edge and slide it back and forth until it stops rocking and sits level; that resting spot is the balance point. Measure the distance from the nock groove (not the very back of the nock itself) to that resting spot in inches, and enter it as Balance Point alongside the arrow's Total Arrow Length measured the same way, from nock groove to the end of the shaft excluding the point.

Easton Archery's own published FOC guidance recommends a 10-15% range for both outdoor target shooting and hunting setups, and this calculator's bands are built around that guidance, extending the hunting-adequate ceiling to 19% since higher FOC keeps improving penetration and down-range stability up to that point, at the cost of some extra trajectory drop and wind drift that matters less for a broadhead-tipped hunting arrow shot at a known distance than for a field-point target arrow. Target archers generally favor the lower end of the ideal range because a flatter, more predictable trajectory matters more when compensating for FOC's minor speed cost, while hunters commonly push toward the upper end of the adequate range for the penetration benefit.

Yes — because FOC only depends on Total Arrow Length and Balance Point, you can model a component swap before buying it: a heavier point pulls the balance point forward and raises FOC, while cutting the shaft shorter without changing the balance point's absolute position raises FOC as well, since it shifts the midpoint closer to the (relatively unchanged) balance point. Re-enter the expected new balance point and length to see the resulting FOC and classification before committing to a build change.