FOC (Front of Center)
FOC stands for Front of Center — the percentage of an arrow's total weight that sits forward of its midpoint. Most archers target 10–15% FOC for a balance between forgiveness, kinetic energy retention at distance, and acceptable trajectory.Detaily
FOC is calculated as ((balance point − arrow length / 2) / arrow length) × 100. The balance point is the spot along the shaft where a built arrow balances on a knife edge; the arrow length is measured from the bottom of the nock groove to the end of the shaft (excluding the point or broadhead).
A higher FOC concentrates mass at the front of the arrow. Forward weight stabilizes the arrow earlier in flight, recovers spine flex faster off the rest, and resists wind drift at distance. The penalty is a slightly higher arc — front-loaded arrows shed velocity more quickly than rear-balanced ones over short ranges, but retain energy better at long ranges.
The 10–15% range is the consensus target for target archery. Bowhunters often push FOC higher — 15–25% — under the Ashby framework, which argues that very-high-FOC heavy arrows penetrate hard tissue more reliably. Below 7% is considered low FOC and tends to produce inconsistent groups and amplified rest-clearance issues.
FOC is changed by adjusting point weight (broadhead or field point), insert weight, or — less commonly — adding internal weight tubes. Heavier nocks, vanes, or wraps move the balance backward and lower FOC. Shaft length itself doesn't change the FOC formula's denominator linearly with the same components, but a longer shaft generally lowers FOC because the same point weight is balancing a longer body.
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- What FOC should I aim for in target archery?
- 10–15% is the consensus range for indoor and outdoor target shooting. Below 10% groups tend to open up at distance; above 15% the arc becomes harder to manage on flat-distance ranges.
- How do I change FOC without changing arrow length?
- Swap to a heavier or lighter point — point weight has the largest single-component impact on FOC. Insert weight is the second-most effective lever. Vane size, wrap presence, and nock weight all shift FOC slightly.
- Why do bowhunters use higher FOC than target archers?
- Heavier-FOC hunting arrows retain more kinetic energy on impact and tend to drive through bone and dense tissue more consistently. The Ashby studies popularized 19%+ FOC for big-game setups, often combined with single-bevel broadheads.