An arrow with more weight at the front flies more stably and penetrates better. Target archers usually aim for 7–15% FOC; hunters often prefer 15% or more (extreme FOC goes above 19%).
How to use the Arrow FOC Calculator
- Arrow length
- Balance point from nock throat
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
Measure the arrow length and the balance point (with the tip installed), both from the nock throat.
Inputs explained
| Field | What to enter |
|---|---|
| Arrow length | Units: in, cm |
| Balance point from nock throat | Units: in, cm |
Example values
How the main result changes when Arrow length changes and everything else stays at the example values above:
| Arrow length (in) | Front of center (FOC) (%) |
|---|---|
| 14.5 | 65.86 |
| 21.75 | 27.24 |
| 29 | 7.93 |
| 36.25 | -3.66 |
| 43.5 | -11.38 |
| 58 | -21.03 |
Formula
FOC (%) = (B − A ÷ 2) ÷ A × 100 (A = arrow length from nock throat to end of shaft, B = distance from nock throat to balance point)
Worked example
Inputs — Arrow length: 29 in; Balance point from nock throat: 16.8 in.
Results — Front of center (FOC) = 7.93 %; Rating = Normal for target archery (7–15%).
Key terms
- Nock throat
- Bottom of the nock groove where the string sits.
Frequently asked questions
How do I find the balance point?
Balance the finished arrow on a knife edge and measure from the nock throat.
How do I increase FOC?
Use a heavier point or insert, or lighter fletching.
Does FOC affect accuracy?
Moderate FOC improves stability; too much can make the arrow nose-dive.
Is it the same for crossbow bolts?
Yes, with the bolt length.