Arrow FOC (Front of Center) Balance Calculator
Calculate the Front of Center (FOC) balance point of your arrow.
Find your FOC percentage and see if it's in the optimal range for accuracy and penetration.
What Is FOC? Front of Center (FOC) is the percentage of an arrow’s balance point measured from the center of the arrow toward the tip. An arrow with the balance point exactly at the center would have 0% FOC. A perfectly front-weighted arrow would have 50% FOC. Real-world arrows should fall in the range of 7–15% FOC for most shooting purposes.
Why FOC Matters The balance point of an arrow determines how it flies and stabilizes after release. An arrow with too little FOC (under 7%) flies erratically — the back end has too much influence. Too much FOC (over 15%) causes the arrow to drop quickly and resist penetrating from steep angles. Optimal FOC creates a self-correcting projectile: if the arrow wobbles, aerodynamic drag on the vanes at the rear corrects the flight.
The FOC Formula FOC (%) = (A − L/2) / L × 100 Where: A = distance from nock groove to balance point (cm or inches) L = total arrow length (cm or inches, measured from nock groove to end of shaft, not including insert)
How to Find the Balance Point Place the arrow horizontally on a thin edge — a pencil works perfectly. Slide it back and forth until the arrow balances horizontally without tilting. Measure from the nock groove to that balance point. That is your value for A.
Recommended FOC Ranges Target archery (field and 3D): 7–11% FOC — flatter trajectory over long distances. Bowhunting with broadheads: 10–15% FOC — better penetration and broadhead stability. Traditional archery: 12–19% FOC — heavier point weights compensate for longer arrows and slower speeds. Competition 3D archery: 9–12% FOC — balanced for accuracy and wind drift resistance.
How to Adjust FOC Increase FOC: add a heavier point/broadhead (grain weight), add an insert with a heavier brass ring, shorten the arrow. Decrease FOC: use a lighter point, add weight to the nock end (lighted nocks add ~25 grains), lengthen the arrow. Every 50-grain increase in point weight adds approximately 1–2% FOC depending on arrow length and weight.
Point Weight and Kinetic Energy Heavier points increase FOC AND add kinetic energy — important for big-game bowhunting. A 100-grain broadhead is standard. Going to 125 grains adds both FOC and penetration. The arrow’s spine must match the draw weight and point weight — heavier points require stiffer spine ratings.