Calculate your arrow's Front of Center (FOC) percentage instantly. Optimize flight stability and perfect bow tuning for target and hunting setups with our free professional FOC tool.
Enter the total length of the arrow (from nock throat to end of shaft) and the distance from the nock to the balance point of the fully assembled arrow.
FOC (Front of Center) determines the stability of the arrow in flight. For target archery, 7-12% is common, while hunters often prefer 12-18% (High FOC) for better penetration and wind stability.
Adjust your FOC by changing the point weight or adding brass inserts. A higher FOC pulls the arrow through the air, similar to a badminton birdie. To find the balance point, balance the assembled arrow on a sharp edge (like a ruler) until it perfectly teeters, then measure the distance from the throat of the nock to that exact spot.
FOC acts as the 'steering' for your arrow. A higher FOC places more weight forward, which helps the fletching stabilize the arrow faster and resist crosswinds better.
Extreme FOC (above 20%) can cause the arrow to 'nose dive' at long ranges and makes the arrow shaft effectively weaker, requiring a stiffer spine adjustment.
You can increase FOC by using a heavier field point or broadhead, adding brass inserts behind the point, or using lighter fletching and nocks at the rear.
FOC percentage equals the balance point distance minus half the arrow length, divided by the full arrow length, times 100. The balance point is measured from the nock throat to the spot where the fully assembled arrow balances. As a worked example, a 30-inch arrow that balances 16.5 inches from the nock gives (16.5 − 15) ÷ 30 × 100 = 5%, a low-FOC arrow.
This calculator sorts your result into four bands. Below 7% is Low, 7% up to 15% is Standard, 15% up to 19% is Extreme FOC (EFOC), and 19% or higher is Ultra-Extreme FOC (UEFOC). Most target archers sit in the Standard range, while many bowhunters chase EFOC for added penetration and forgiveness in wind, accepting slightly more long-range drop in return.