Archery
FOC Calculator
Calculate the Front of Center (FOC%) of your arrow. Two modes: "Measure" from an assembled arrow, or "Plan" from individual component weights.
✓ Measure mode
✓ Build planner mode
✓ Category indicator (Target → EFOC)
✓ FOC range reference
✓ Auto balance-point estimation
How to use
- 1 Pick a mode (Measure or Plan)
- 2 Measure: enter arrow length and balance point distance
- 3 Plan: enter shaft, point, insert, nock, and vane weights
- 4 Result: FOC%, category, and reference range update instantly
From throat of nock to end of shaft (excluding the point)
Distance from throat of nock to where the arrow balances
Result
FOC
8.62%
Category
Target7–12%. Typical for recurve and compound target archery
Arrow visualization
Visual layout of nock, vanes, shaft, insert, and point — with the arrow center (L/2) and balance point (A) marked.
Nock
Vanes
Shaft
Insert
Point
FOC range reference
| FOC | Category | Note |
|---|---|---|
| < 7% | Low FOC | Inconsistent flight — add front weight |
| 7–12% | Target | Standard for recurve / compound target |
| 12–15% | Hunting std. | Standard for 3D / field / hunting |
| 15–19% | High FOC | Penetration-focused hunting |
| ≥ 19% | EFOC | Ashby extreme FOC for large game |
💡 Tips
- ・FOC% = (A − L/2) / L × 100. L is throat of nock to end of shaft (excluding the point).
- ・For measure mode, balance the arrow on a finger or string to find the balance point.
- ・Changing point weight by 10 gn typically shifts FOC by 0.5–1%.
- ・To raise FOC without changing spine: heavier point + stiffer spine shaft.
- ・For target archery, FOC around 10–12% is typical.