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Crossbow glossary

What Is FOC (Front of Center)?

FOC (Front of Center): The percentage of a bolt’s weight that sits ahead of its midpoint.

By Marisol Vega, Senior Outdoor Equipment Writer & Research Editor. Manufacturer figures vary; check your crossbow's manual.

FOC describes balance. A higher front-of-center percentage means more of the bolt’s weight is forward of the center point, which affects flight stability and how the bolt behaves with a given tip weight.

It is calculated from the bolt’s balance point and length. Changing tip weight is the usual way to adjust it.

Calculating FOC

FOC % = ((balance point from nock − bolt length ÷ 2) ÷ bolt length) × 100

A 20-inch bolt that balances 11.5 inches from the nock: (11.5 − 10) ÷ 20 × 100 = 7.5% FOC. Adding tip weight moves the balance point forward and raises the figure.

Why FOC matters

FOC describes how a bolt is balanced. More weight forward tends to stabilise flight, especially with broadheads, which catch air differently from field points.

Because tip weight is easy to change, FOC is one of the few bolt variables you can tune yourself.

How to read it on a spec sheet

  • Measure the balance point by resting the bolt on a narrow edge and finding where it balances, then apply the formula above.
  • Compare FOC between field points and broadheads. Different tips change the number.

Common mistakes

  • Adding tip weight without checking that the bolt still meets the crossbow’s minimum weight and length.
  • Chasing a high FOC figure without checking how the bolt actually groups.

Frequently asked questions

What is a good FOC for crossbow bolts?

It depends on the bolt, tip and crossbow. Bolt makers publish their own guidance; test groups with your setup rather than aiming at a number.

How do I raise FOC?

Use a heavier tip or insert. Stay within the crossbow maker’s limits for bolt weight.

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Definitions are general information. Always follow your crossbow manufacturer's manual, and verify local laws with the relevant authority.