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Arrow Balance and Front-of-Center
Calculate the balance-point offset from an arrow shaft midpoint, as a percentage of measured shaft length.
- Formula & worked example
- Private in your browser
- No signup
Calculator inputs
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How to use this calculator
- Enter the known values in the units shown. Results update as you type.
- Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
- Use the worked example to check the method. Reset restores the starting fields.
Private by default
Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.
Formula and method
A 100 cm arrow balancing at 60 cm has 10% front-of-center.
FOC = 100 × (balance distance − length/2)/length.
Worked example
Enter these known values and leave the other values blank.
- Arrow's length (A)
- 100 cm
- Length to balance point (B)
- 60 cm
- Front-of-center (FOC)
- 10 %
Assumptions and limitations
- Measure both distances from the bottom of the nock groove. Shaft length ends at the shaft end; balance is measured with the assembled arrow. The calculation describes balance geometry and does not certify tuning, spine or shooting suitability.
- Clear an unknown before solving an available inverse branch, and lock independent known values when comparing measurements. Use compatible units; a one-way score or lookup does not supply an inverse.
Common questions
What does this result represent?
Measure both distances from the bottom of the nock groove. Shaft length ends at the shaft end; balance is measured with the assembled arrow. The calculation describes balance geometry and does not certify tuning, spine or shooting suitability.
Can I work backward from an answer?
Where the captured equation supplies an inverse, clear the unknown and enter independent known values. Rounded scores, one-way outputs and fixed lookup choices do not uniquely recover inputs.
References
Restrict the measured balance point to the shaft segment, while allowing signed front-of-center offsets. Replace the external arrow illustration with original accessible measurement instructions for shaft length, midpoint and signed balance offset, preserving all image identities and conditions.