arrow foc calculator

What Is Arrow FOC?

FOC stands for Front of Center. It tells you how far the arrow’s balance point sits in front of the arrow’s midpoint. In plain terms, it describes how front-heavy your arrow is.

Archers use FOC to tune arrow flight and optimize performance for target shooting, 3D, and hunting setups. A balanced FOC can improve consistency, while very high or very low FOC can change how an arrow recovers from paradox, penetrates, and groups downrange.

FOC Formula

The standard formula is:

FOC % = ((Balance Point − (Arrow Length ÷ 2)) ÷ Arrow Length) × 100

Both measurements must use the same unit (inches recommended), and both should be measured from the nock throat.

Quick Example

• Arrow length: 29.0 in
• Balance point: 19.0 in
• Midpoint: 14.5 in

FOC = ((19.0 − 14.5) ÷ 29.0) × 100 = 15.52%

How to Measure Correctly

• Assemble the arrow exactly as you shoot it (point/broadhead, insert, nock, vanes, wrap, everything).
• Measure arrow length from the nock throat to the end of the shaft.
• Balance the arrow on a sharp edge or balancing tool and mark the balance point.
• Measure from nock throat to that balance point.
• Enter both values into the calculator.

What Is a Good FOC for Arrows?

“Good” depends on your use case, bow tune, and distance. These are common reference ranges:

FOC Range	General Interpretation
Below 7%	Low FOC; may be less forgiving in some setups
7% – 12%	Typical for many target and general-purpose arrows
12% – 18%	Higher FOC; common in many hunting arrow builds
Above 18%	Very high / extreme FOC; can work, but tune and trajectory trade-offs matter

How to Increase or Decrease FOC

To Increase FOC

• Use a heavier point or broadhead.
• Add brass inserts or heavier outserts.
• Use lighter nocks/vanes if possible.
• Shorten shaft length only when safe and appropriate for your draw length.

To Decrease FOC

• Use a lighter point or insert system.
• Add rear weight (heavier vanes, wraps, or nock systems).
• Use a slightly longer shaft if your setup allows.

Common Mistakes to Avoid

• Measuring a bare shaft instead of a fully built arrow.
• Mixing measurement references (shaft end vs. nock throat).
• Using inconsistent units.
• Changing multiple arrow components at once and losing track of results.
• Focusing only on FOC instead of broadhead flight, paper tune, and real grouping results.

FAQ

Does higher FOC always mean better penetration?

Not always. Penetration depends on total arrow mass, broadhead design, arrow straightness, impact angle, and tune quality in addition to FOC.

Can target archers use high FOC?

Yes, but most target shooters prioritize consistency and wind behavior for their discipline. Many stay in moderate FOC ranges.

Should I tune by FOC only?

No. Use FOC as one variable in a complete arrow setup process that includes spine, point weight, bow tune, and field-point/broadhead grouping.

If you want repeatable results, track each build in a notebook: shaft model, cut length, insert weight, point weight, nock, vane type, and final FOC. This makes future tuning faster and more predictable.