Navy Body Fat Calculator
Body fat percentage from neck, waist and hip measurements — the US Navy circumference method, with its accuracy stated honestly.
The Navy method uses a logarithmic regression on circumferences and height.
How the navy body fat calculator works
The Navy method uses a logarithmic regression on circumferences and height. For men it needs neck and waist; for women it adds the hip. It was developed to be usable with a tape measure and no equipment.
Its accuracy against a DEXA scan is about ±3 to 4 percentage points, which is worse than it looks and better than nothing. Its real value is tracking change: measure the same way each time, and the trend is far more reliable than the absolute number.
Formula: men: 495/(1.0324 − 0.19077 log(waist−neck) + 0.15456 log(height)) − 450
Worked examples
| Inputs | Body fat | Note |
|---|---|---|
| Male, 178 cm, 38 neck, 88 waist | 18.7% | about 21% |
| Female with hip measurement | 29.43% | about 29% |
| A leaner male | 8.82% | about 13% |
FAQFrequently asked questions
How accurate is the Navy method?
About ±3 to 4 percentage points against a DEXA scan. That is a wide margin, so treat the number as approximate.
Where do I measure?
Neck below the larynx, waist at the navel for men and at the narrowest point for women, hips at the widest point. Keep the tape level and snug without compressing.
Why do women need a hip measurement?
Because female fat distribution includes the hips and thighs, which the male formula would miss entirely.
What body fat percentage should I aim for?
8 to 19% for men aged 20 to 39, 21 to 33% for women. Athletes sit lower; below the essential level (about 5% and 12%) is harmful.
Is it better than BMI?
For body composition, yes, because it distinguishes fat from lean mass at all. For tracking change over time it is better again — measure the same way each time.
Where these figures come from
- Mifflin MD et al., "A new predictive equation for resting energy expenditure in healthy individuals", Am J Clin Nutr 1990 — the BMR equation used here
- World Health Organization — Waist circumference and waist–hip ratio (2008 expert consultation) — waist-to-hip cut-offs
- Tanaka H, Monahan KD, Seals DR, "Age-predicted maximal heart rate revisited", J Am Coll Cardiol 2001 — 208 − 0.7 × age
- Nathan DM et al., "Translating the A1C assay into estimated average glucose values" (ADAG), Diabetes Care 2008 — eAG = 28.7 × A1c − 46.7
- Mosteller RD, "Simplified calculation of body-surface area", N Engl J Med 1987 — BSA = √(height × weight / 3600)
- NHS — national health guidance
Last checked: September 2026. The equations are fixed by their published papers and do not change with tax years or regulations; the thresholds quoted in verdicts name the body that set them.