Arrow FOC Calculator
Calculator
Use this arrow FOC calculator to estimate front-of-center percentage from arrow length and balance point. It is one part of tuning, not a magic accuracy fix, and it works best after the arrow length and spine are already close.
Estimate FOC percentage
Formula: FOC % = ((balance point – half arrow length) ÷ arrow length) × 100
Measure a finished arrow, find the balance point from the nock throat, and keep the method consistent every time.
- Use a finished arrow, not a bare shaft.
- Measure from the nock throat to the balance point.
- Keep the method the same each time.
- Weighing the finished arrow and checking spine still matter after you get the FOC number.
How to measure balance point
Do not change the method from one arrow to the next if you want a useful comparison.
Formula used
FOC % = ((balance point - half arrow length) ÷ arrow length) × 100
Half arrow length is simply arrow length divided by two.
Example calculation
This example uses the numbers from the formula so you can check the math by hand.
| Item | Value |
|---|---|
| Arrow length | 29 inches |
| Balance point | 17 inches from nock throat |
| Half length | 14.5 inches |
| FOC | 8.6% |
A stable method matters more than chasing a single number.
What FOC affects
- Arrow balance.
- Broadhead flight.
- Tuning.
- Downrange behavior.
- How the arrow reacts to the rest of the setup.
FOC can help or hurt depending on the full setup, so do not treat it as a standalone accuracy fix.
FOC and arrow setup
- Heavier points usually increase FOC.
- Insert and outsert weight can also push FOC forward.
- Heavier rear components can reduce FOC.
- Changing FOC also changes total arrow weight and dynamic spine behavior.
- Use the Arrow Weight Calculator and Arrow Spine Chart with the FOC number, not instead of them.
Common mistakes
- Measuring from the wrong point.
- Using unfinished arrows.
- Ignoring insert or outsert weight.
- Chasing high FOC without tuning.
- Comparing numbers measured with different methods.
- Ignoring manufacturer arrow guidance.
Related guides
Use these pages to keep the arrow setup path together.
Frequently asked questions
Short answers for common FOC questions.
What does FOC mean on an arrow?
FOC means front of center. It tells you how far the arrow’s balance point sits in front of the middle of the shaft.
How do you calculate arrow FOC?
Use the arrow length and the balance point from the nock throat, then apply the FOC formula on this page.
What is a good arrow FOC?
It depends on the setup and use. The calculator gives a number, but the right value still depends on the full arrow and bow setup.
Does heavier point weight increase FOC?
Usually yes. More front weight moves the balance point forward and can raise FOC.
Is higher FOC always better?
No. Higher FOC can help in some setups, but it is not a magic accuracy fix and it can also change tuning.
Should beginners worry about FOC?
Only after the arrow length, spine, and safe setup are already close. Beginners should not chase FOC before the basics.
Is FOC the same as arrow spine?
No. FOC is balance. Spine is stiffness. They affect different parts of tuning and flight.
References
These references support the FOC and arrow-balance guidance used here.
- Easton Archery — FAQ’s about Arrow F.O.C. (Front of Center)
- Easton Archery — What is F.O.C. and how does it affect arrow flight?
- Gold Tip Calculator
- Victory Archery FOC Calculator