Arrow FOC Calculator
Find an arrow's front-of-center (FOC) balance percentage.
FOC is how far an arrow's balance point sits ahead of its center — it affects flight and penetration.
How the Math Works
The Arrow FOC Calculator uses a straightforward mathematical formula to determine front-of-center balance: FOC = (balance - length/2) / length × 100. This equation measures how far forward the arrow's center of balance sits relative to its midpoint. The 'balance' value represents where the arrow naturally rests when suspended, while 'length' is the total arrow length. By subtracting half the length (the midpoint) from the balance point and dividing by the full length, we get a decimal that converts to a percentage showing how much of the arrow's weight is concentrated in front of its center.
Practical Applications
To use this calculator practically, first measure your arrow's total length in inches. Then suspend the arrow freely by placing it on two fingertips or a narrow support, letting it rest naturally. Mark or measure the exact point where the arrow balances horizontally - this is your balance point. Measure from the same reference point used for length (typically the back end) to this balance mark. Input these two measurements into the calculator to instantly determine your arrow's FOC percentage, which helps you make informed decisions about point weight and arrow spine selection for optimal flight performance.
Day-to-Day Use
Knowing your arrow's front-of-center percentage directly impacts your archery success in everyday shooting. Arrows with higher FOC (typically 15-20%) fly more stably through wind and deliver more consistent accuracy at distance, making them ideal for hunting or competition. Lower FOC arrows (10-15%) may fly faster but can be less stable. This simple calculation helps you choose the right arrows for your specific bow setup, improve your shooting consistency without expensive trial-and-error, and understand why some arrows outperform others in your local shooting environment - whether that's a calm backyard range or windy outdoor hunting grounds.
Worked example
29" arrow balancing at 16.5" → about 6.9% FOC.
FAQ
What FOC is ideal?
Roughly 7–15% for hunting; higher FOC improves penetration but lowers speed.