Calculate finished-arrow front-of-center percentage, balance-point distance, or arrow length using one consistent nock-throat measurement origin.
Arrow Front-of-Center Formula
FOC expresses how far the finished arrow's balance point lies ahead of its geometric midpoint as a percentage of shaft length.
How the Calculation Works
Choose the output in Solve for and enter the visible source values. Values are retained when switching modes. Distance unit changes convert an entered measurement.
How to Use This Calculator
- Select the value or workflow you want in the Solve for menu.
- Enter only the visible source values and use the units shown beside them.
- Select Calculate and review the primary answer, supporting values, warning, and steps.
- Use Reset before starting a different bow, arrow, or round.
Worked Example
A 30-inch arrow balancing 18 inches from the nock throat has 10.00% FOC: 100 x (18 - 15) / 30.
Input and Result Guide
| Item | How to use it |
|---|---|
| Arrow length | Measure from the throat of the nock to the shaft end; exclude the point or broadhead. |
| Balance point | Measure from that same nock-throat origin to the finished arrow's balance point. |
| Units | Choose each distance unit; the calculator converts them to a common unit. |
| FOC | Positive values place the balance point in front of the midpoint. |
| Typical context | Manufacturer guidance often discusses roughly 10-15% for hunting, but the exact setup controls. |
Interpreting the Result
FOC is one build characteristic. Compare values only when the same measurement convention and complete installed components are used.
Assumptions and Limitations
Do not treat a preferred band as universal. Arrow length, broadhead, shaft design, total weight, tune, clearance, and intended use all matter.
Common Questions
Why did a field disappear after I changed Solve for?
A hidden field is either the requested output or irrelevant to the selected workflow. Enter the remaining visible source values.
Will my last successful calculation be restored?
Yes. The calculator saves the successful input snapshot in this browser and recomputes the result on return. Reset clears that saved state.
Sources
Easton Archery, FOC formula, measurement convention, and arrow-selection FAQs.
