Arrow FOC Calculator (Front of Center)

How it works

FOC % = 100 × (balance point − length ÷ 2) ÷ length (AMO: length from nock groove to end of shaft, balance point measured with the point on)

Front-of-center describes how far forward an arrow’s balance point sits relative to its middle, and it governs how the arrow flies: a nose-heavy arrow straightens out faster off the bow and resists wind and broadhead steering, while a balanced arrow flies flatter and faster. The Archery Trade Association’s method measures length from the nock groove to the end of the shaft and the balance point with the point installed; a result of 7–11% suits target and 3D shooting, 10–15% is the sweet spot for most compound hunting set-ups, and traditional and heavy-arrow hunters push to 15–20% or more for penetration. Because FOC and spine interact — a heavier point weakens the effective spine — changing point weight usually means re-checking arrow flight or bare-shaft tuning.

Worked example

A 29″ arrow balancing at 18.25″: (18.25 − 14.5) ÷ 29 = 12.9% FOC — squarely in the hunting range. Moving from a 100 to a 125 grain point pushes it to about 15.4%.

Frequently asked questions