Arrow FOC Calculator

FOC stands for Front of Center, and it describes how far the arrow's center of gravity sits in front of the physical center of the arrow's length. A higher FOC means more weight toward the tip, which improves arrow stability and penetration. A properly balanced hunting or target arrow typically has an FOC between 7% and 15%.

The AMO (Archery Manufacturers and Merchants Organization) standard formula is: %FOC = (100 × (B − A/2)) / A, where A is the total arrow length and B is the distance from the nock groove to the balance point. This is the universally accepted method used by all major archery manufacturers.

Fully assemble your arrow with all components (point, nock, vanes, wraps). Then rest it on a single finger and slide your finger until the arrow balances horizontally without tipping. Measure the distance from the nock groove to that balance point — that's your balance point length (B).

Most bowhunters aim for an FOC between 10% and 15% for hunting setups. Higher FOC (15%+) can improve penetration and accuracy at longer distances but may affect arrow flight. For target archery, a range of 7%–12% is generally preferred to maximize trajectory performance.

The most effective way to increase FOC is to add weight to the front of the arrow — switching to a heavier field point or broadhead, using a heavier insert, or adding a brass insert collar. Reducing weight at the rear (lighter nock or fewer/shorter vanes) also increases FOC.

Yes. A longer arrow shaft shifts the physical center of the arrow further back, meaning the same balance point results in a lower FOC percentage. When cutting arrows shorter, your FOC percentage will change even if you haven't changed any components — always recalculate after resizing your shafts.

Arrow length (A) is the full assembled length measured from the nock groove to the end of the shaft (not including the point). Shaft length refers to just the bare carbon or aluminum tube. For the FOC formula, always use the full assembled arrow length measured from nock to shaft tip.

Yes — an excessively high FOC (above 19%–20%) can cause the arrow to nose-dive in flight, reducing trajectory and making tuning more difficult. For most compound bow setups, staying within the 10%–15% range offers the best balance of stability, penetration, and accuracy.