The F.O.C. (Forward of Center) Calculator is designed for archers, bowhunters, and arrow builders to determine the optimal balance point of an arrow. The F.O.C. value tells how far forward the arrow’s center of mass is from its midpoint. This measurement is crucial because it directly affects the arrow’s flight, penetration, and overall stability.
Having a well-balanced arrow improves accuracy and consistency, especially over longer distances. A higher F.O.C. often means better front-end control, which helps the arrow stay on course after being released. This calculator simplifies the process by automatically computing the F.O.C. percentage based on the arrow’s measurements, ensuring users can make quick, informed adjustments to their gear.
formula
F.O.C. (%) = [(Balance Point − Arrow Midpoint) / Arrow Length] × 100
Where:
Balance Point = Distance from the nock end to the arrow’s center of mass
Arrow Midpoint = Arrow Length / 2
Arrow Length = Distance from the nock groove to the end of the shaft (not including the point)
This result gives the Forward of Center percentage. A typical hunting arrow might have an F.O.C. between 10–15%, while target arrows may have a lower value for flatter trajectory.
Common Arrow Balancing Terms and Quick Reference
| Term | Description |
|---|---|
| F.O.C. | Forward of Center, indicates front-loaded weight balance |
| Arrow Length | Measured from the bottom of the nock groove to the shaft’s end |
| Balance Point | Point along the arrow where it balances horizontally |
| Optimal F.O.C. | For hunting: 10–15%, For target: 7–10% |
| Higher F.O.C. | More front weight, better penetration and stability in wind |
| Lower F.O.C. | Less front weight, flatter trajectory, better for target shooting |
This table helps users quickly identify which terms matter and how to interpret their results.
Example
Let’s say an archer is working with an arrow that is 30 inches long. They find the balance point of the arrow is 19.5 inches from the nock groove.
Step 1: Calculate Arrow Midpoint
Midpoint = Arrow Length / 2 = 30 / 2 = 15 inches
Step 2: Apply the Formula
F.O.C. = [(19.5 − 15) / 30] × 100
F.O.C. = (4.5 / 30) × 100 = 0.15 × 100 = 15%
The result is a 15% F.O.C., which is considered ideal for most hunting setups, offering excellent stability and good downrange control.
Most Common FAQs
F.O.C. helps balance the arrow properly, improving its flight stability, accuracy, and how deeply it penetrates the target.
A typical range is between 10% and 15%. This ensures enough front-end weight for controlled flight and strong impact.
To increase F.O.C., use heavier points or inserts at the front of the arrow, or reduce rear weight by using lighter vanes or nocks.