Methodology: Body Fat Percentage Calculator

Scope

Estimates body fat percentage using the U.S. Navy circumference method.

Formula

Men: %BF = 86.010*log10(abdomen - neck) - 70.041*log10(height) + 36.76. Women: %BF = 163.205*log10(waist + hip - neck) - 97.684*log10(height) - 78.387.

Coefficients

Parameter	Value	Note
Inputs	`Neck, waist/abdomen, hip (F), height`
Units	`inches (formula native)`

Data sources

Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy men and women from body circumferences and height. Naval Health Research Center, 1984. Report 84-11 & 84-29.

Assumptions

Tape measurements are taken at the anatomical landmarks specified by the original Navy protocol.

Approximation range

Typical RMSE vs DXA: 3–4 percentage points for adults inside the Navy cohort's demographic range.

Limitations

Heavily influenced by abdominal girth; very muscular midsections or unusually wide shoulders mis-predict.
Female formula requires consistent measurement of the hip's widest point; user error dominates residuals.

Reproducibility

Male, height 70 in, neck 16, abdomen 35: %BF = 86.010*log10(35-16) - 70.041*log10(70) + 36.76 ≈ 15.8%.

Change log

2026-04-24: methodology page first published.

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