# Arrow FOC Calculator (Front of Center)

URL: https://speedycalculator.com/calculators/sports/foc/
Last updated: 2026-10-30

> The FOC calculator works out an arrow's front-of-center balance – how far the balance point sits ahead of the middle of the arrow, as a percentage of its length – and rates it for target shooting or hunting.

## Inputs

- Arrow length (in, cm)
- Balance point from nock throat (in, cm)

## Results

- Front of center (FOC)
- Rating

## 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)
```

## Explanation

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

FieldWhat to enterArrow lengthUnits: in, cmBalance point from nock throatUnits: 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) (%)14.565.8621.7527.24297.9336.25-3.6643.5-11.3858-21.03

## 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.

## FAQ

**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.


## Sources

- [Easton Archery – Arrow tuning and FOC](https://eastonarchery.com/)
- [Ashby Bowhunting Foundation – EFOC study](https://www.ashbybowhunting.com/)