Arrow FOC Calculator

This arrow FOC calculator works out the front of centre balance of a finished arrow, the single number that tells you how far forward the weight sits along the shaft. FOC, short for front of centre, matters because an arrow that is nose-heavy steers and recovers from the bow more cleanly, which usually means tighter groups and better penetration, while an arrow that balances too far back can fly erratically. You need just two measurements: the arrow length, taken from the throat of the nock to the end of the shaft and not counting the point, and the balance point, which is where the completed arrow, with point, insert, vanes and nock fitted, balances on an edge, measured from the same throat of the nock. The calculator subtracts the physical centre of the shaft from the balance point, divides by the length, and expresses the result as a percentage. It also shows the centre point of the shaft and how far ahead of it your balance sits, so you can see exactly what is driving the number. Target and field archers often run around 7 to 12 percent, while many bowhunters prefer 10 to 15 percent for heavier hitting arrows. Enter your two measurements in inches to see your FOC, with a worked example below. Use it to compare shafts, points and inserts as you tune a new setup.

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An FOC of 7.5% sits within the commonly recommended 7 to 15% range, giving a good balance of forgiveness and trajectory.

Measure the arrow length from the throat of the nock to the end of the shaft, excluding the point, and take the balance point on the finished arrow. FOC is a guide to flight, not a rule: tune to your own bow and distance.