Front of Center and the Crossbow Arrow

What Is FOC?

Front of Center (FOC) weight in a crossbow arrow means that the front of the arrow is heavier than the rear of the arrow in relationship to its mid-point.

Why Is FOC Significant to Crossbow Shooters?

Crossbow arrows are typically 20- to 22 inches in length. The shorter the arrow, the more prone the arrow is to oscillate which causes erratic flight. Establishing the proper FOC weight of your arrow in conjunction with your current crossbow will eliminate poor arrow flight.

How to Calculate FOC

Measure the overall length of the arrow from its tip to nock point. That value is OAL. If the overall length of the arrow is 22 inches, then the center point is now established at 11 inches. That value is OAL/2.

Next find the exact balance point of the arrow by balancing the arrow on a very narrow edge. Mark the arrow at its precise balance point. That value is BP.

Divide the balance point (BP) by the overall arrow length (OAL). Subtract this value by (OAL/2) and then multiply that result by 100. The final number is your Front of Center (FOC).

BP divided by OAL OAL/2 x 100 = FOC.

A common FOC for a crossbow arrow is between 16 and 22 percent. Adjusting an arrow's FOC is done by changing tip weights, inserts and/or fletching.