Formula, in Body Composition

Body Fat Percentage Formula (US Navy)

The US Navy method estimates body fat from neck, waist, and (for women) hip circumferences. It's a regression equation, not a direct measurement, so expect ±3% accuracy versus DXA.

5 variables. Published Mar 12, 2026. Updated May 10, 2026. By AI Fit Hub.

Education, not medical advice. The result comes only from the published formula and your inputs. How we check our formulas.

Formula

Male:   BF% = 86.010·log10(waist − neck) − 70.041·log10(height) + 36.76
Female: BF% = 163.205·log10(waist + hip − neck) − 97.684·log10(height) − 78.387
(all measurements in centimeters)

Variables

BF%

Body fat percentage

Fat mass as a percentage of total body mass. Reference ranges: men 10–22% (essential fat 2–5%), women 18–32% (essential 10–13%).

neck

Neck circumference

Measure below the larynx, perpendicular to the long axis of the neck. Centimeters.

waist

Waist circumference

Men: at the navel. Women: at the narrowest point above the navel. Measure on an exhale, no compression.

hip

Hip circumference (women only)

At the widest point of the buttocks.

height

Standing height

Centimeters, barefoot.

Step by step

1

Take all measurements with a flexible non-stretch tape, on a relaxed exhale. Repeat each three times and average.

Neck: 38.5, 38.0, 38.2 → 38.2 cm.
2

Compute the circumference difference: waist minus neck (men) or waist plus hip minus neck (women).

Male: waist 84 − neck 38 = 46 cm.
3

Apply the log10 terms. log10(46) ≈ 1.663; log10(178) ≈ 2.250.

Male: 86.010·1.663 − 70.041·2.250 + 36.76.
4

Sum the terms.

143.04 − 157.59 + 36.76 = 22.2% body fat.

Worked example

Male, 178 cm, neck 38 cm, waist 84 cm

Sex

Male

Height (cm)

178

Neck (cm)

Waist (cm)

BF% = 86.010·log10(84 − 38) − 70.041·log10(178) + 36.76 = 86.010·1.663 − 70.041·2.250 + 36.76 = 143.04 − 157.59 + 36.76

Body fat ~22.2%. Mid-range for an average male; lean for a trained one.

Common variations

DXA (dual-energy X-ray absorptiometry) is the most accurate non-invasive method, ±1% vs. cadaver dissection.

Skinfold caliper methods (Jackson-Pollock 3-site or 7-site) cost less but require trained technique; ±3–4% accuracy.

Bioelectrical impedance (handheld or scale) is heavily affected by hydration — useful for trend tracking only.

Run the numbers next

Body Composition Lean Body Mass Calculator
Estimate lean body mass using Boer, James, and Hume formulas from height and weight.
Body Composition Waist-to-Hip Ratio Calculator
Calculate waist-to-hip ratio and assess body composition using WHO guidelines.

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, Report 84-11
Body composition methods: comparisons and interpretation , Journal of Diabetes Science and Technology (2008) — Duren et al.