Last updated 3 September 2026
How the US Navy method works
Rather than pinching skinfolds with calipers, this method uses circumference measurements — waist, neck, and for women, hip — combined with height in a formula developed for the US Navy. It is an estimate from a tape measure, not a measurement. Published comparisons against DEXA scanning report average differences of roughly two to three percentage points in either direction, with a wider spread for individuals, and the same research questions how precise the method is at the individual level. Use it to track direction over time rather than as an exact figure.
Measuring correctly
- Neck — just below the larynx (Adam's apple), tape sloping slightly downward at the front.
- Waist — at the narrowest point, roughly navel height, without pulling the tape tight enough to compress the skin.
- Hip (women) — at the widest point around the hips and glutes.
Method, limitations and sources
Formula. This calculator uses the US Navy circumference method (Hodgdon and Beckett, Naval Health Research Center, 1984), which estimates body-fat percentage from a logarithmic combination of tape measurements and height. Men: waist minus neck, plus height. Women: waist plus hip minus neck, plus height.
Inputs it needs. Sex, height, neck and waist circumference, plus hip circumference for women. Nothing else is used — weight is not part of this formula.
What it assumes. That fat is distributed in roughly the pattern the original US Navy sample showed, and that your measurements were taken at the standard sites with the tape snug but not compressing the skin. Small measuring errors move the result by more than people expect: a centimetre at the waist can shift the estimate by around a percentage point.
Where it is least reliable. Very muscular people, people carrying a lot of fat, athletes, pregnant women, children and teenagers, and anyone whose body proportions sit outside the original military sample. The formula was derived on adult US service members, so it does not represent every population equally.
When not to use it. Do not use this figure to diagnose anything, to set an aggressive weight-loss target, or in place of a clinical assessment. A DEXA scan, hydrostatic weighing or a clinician’s assessment will always be better evidence than a tape measure.
- CDC — About Body Mass Index, on why single-number body measures are screening tools rather than diagnoses.
- 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 No. 84-11 / 84-29, 1984 — the original derivation of this formula.
Common questions
How accurate is the US Navy method?
It is an estimate, not a measurement. Published comparisons against DEXA scanning report average differences of roughly two to three percentage points in either direction, with a noticeably wider spread for any one person. Accuracy falls away at the very lean and very heavy ends, and for people with high muscle mass or unusual proportions. Its real advantage is that it needs only a tape measure and gives repeatable numbers you can compare over time.
How do I measure my waist and neck correctly?
Measure the neck just below the larynx, and the waist at the narrowest point (roughly navel height) without pulling the tape tight enough to compress the skin. For women, the hip measurement is taken at the widest point.
Is this medical advice?
No. It's a general estimate from a standard formula, not a diagnosis. Body composition varies for reasons this calculator can't see, and a healthy body comes in many shapes — speak to a doctor for anything specific to your health.