Arrow FOC Calculator
Calculate arrow Front of Center for optimal performance
How to Use
- Measure your arrow's total length from nock groove to end of shaft
- Find the balance point by balancing arrow on a ruler or edge
- Measure distance from nock groove to balance point
- Enter both measurements in the same unit
- Click calculate to see your FOC percentage and classification
What is Front of Center (FOC)?
Front of Center (FOC) is a measurement that expresses how far forward the balance point of an arrow is from its physical center. It's calculated as a percentage and is crucial for arrow flight performance, accuracy, and penetration.
FOC is calculated using the formula: FOC% = ((Balance Point - (Arrow Length / 2)) / Arrow Length) × 100. A positive percentage means the arrow is front-weighted, while negative indicates rear-weighted (which should be avoided).
FOC Classification Ranges
Different FOC percentages are suited for different archery applications:
| FOC Range | Classification | Best Use |
|---|---|---|
| Below 0% | Rear-Weighted | Dangerous - avoid completely |
| 0-6% | Neutral | Target archery, 3D competition |
| 7-10% | Moderate | Target archery, small game hunting |
| 11-15% | High | Hunting, big game |
| 16%+ | Extreme | Heavy bone, dangerous game |
How to Measure FOC Accurately
To measure FOC accurately, follow these steps:
- Assemble arrow completely with nock, vanes/fletching, insert, and field point/broadhead
- Measure total arrow length from the bottom of the nock groove to the end of the shaft (not including point)
- Balance the arrow on a ruler, table edge, or dedicated balance tool
- Measure from the nock groove to the balance point
- Use the same units for both measurements
- Ensure arrow is dry and at room temperature for consistent results
How to Adjust FOC
To increase FOC (add front weight):
- Use heavier field points or broadheads
- Add weight tubes or inserts behind the point
- Use brass inserts instead of aluminum
- Add point weight collars or weight rings
To decrease FOC (reduce front weight):
- Use lighter points
- Switch to lighter vanes or smaller fletching
- Use lighter nocks
- Remove unnecessary weight from front
Benefits of Proper FOC
Proper FOC provides several performance benefits:
- Improved arrow flight stability and consistency
- Better downrange accuracy and tighter groups
- Increased penetration on game animals
- More forgiving of shooting form errors
- Reduced wind drift and better trajectory
- Better performance with fixed-blade broadheads
- Quieter arrow flight
Frequently Asked Questions
- What FOC percentage should I use for hunting?
- For hunting, 10-15% FOC is ideal for most situations. This range provides excellent penetration, accuracy, and forgiveness. Big game hunters often prefer 12-15% or higher for maximum bone-breaking penetration. For small game or 3D archery, 7-10% works well.
- How do I measure the balance point accurately?
- Place your fully assembled arrow (with point, nock, and vanes) on a ruler edge, pencil, or your finger. Slide it until it balances evenly. The balance point is where the arrow sits level without tipping. Measure from the nock groove (not the back of the nock) to this point.
- Can FOC be too high?
- Very high FOC (16%+) maximizes penetration but may reduce arrow speed and flatten trajectory. For most hunters, 10-15% offers the best balance. Extreme FOC (20%+) is used by some traditional bowhunters for dangerous game but requires proper tuning and may affect downrange velocity.
- Why is my arrow rear-weighted?
- Rear-weighted arrows indicate a problem - likely missing the field point, using an extremely light point, or measurement error. This is dangerous and causes erratic flight. Check that all components are installed correctly and remeasure. Arrows should never be rear-weighted.