Body Fat Percentage Calculator
Estimate body fat percentage using the US Navy tape-measure method.
Measure waist at the navel, neck just below the larynx.
Estimated body fat
—
Population-level screening estimates — not medical advice or a diagnosis. Talk to a doctor or dietitian before acting on a result, especially one that concerns you. Full disclaimer.
About this tool
Estimates body fat percentage from a few tape-measure circumferences using the US Navy method. It needs no calipers, scale, or scan — just a soft measuring tape — which is why it's widely used for a quick figure. It is an estimate, not a measurement.
How the method works. The US Navy (Hodgdon–Beckett) equations take the log of the difference between your waist and neck circumference — the parts of the body where fat and lean tissue differ most — scaled by height. Women's bodies distribute fat differently, so the female equation also uses hip circumference. The result is fed through the Siri equation to convert body density into a fat percentage.
Measuring correctly matters more than the formula. A 1 cm error on the waist can shift the result by 1–2 percentage points.
- Neck: just below the larynx (Adam's apple), tape sloping slightly down to the front.
- Waist: at the navel for men; at the narrowest point for women. Relax, don't suck in, measure after a normal exhale.
- Hip (women): around the widest part of the buttocks.
- Keep the tape level and snug but not compressing the skin. Measure twice and average.
Typical categories (American Council on Exercise):
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletes | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Acceptable | 18–24% | 25–31% |
| Above range | 25%+ | 32%+ |
Accuracy. For an average person the tape method is usually within about 3 percentage points of a DEXA scan. It's least reliable at the extremes — very lean or very muscular people, whose waist-to-neck relationship doesn't follow the population pattern the equations were fitted to. Use it for tracking a trend in yourself over weeks, not as an exact number to compare against someone else.
More accurate methods, in rough order: DEXA scan, hydrostatic (underwater) weighing, air-displacement (Bod Pod), multi-site skinfold calipers by a trained tester, bioelectrical impedance scales (convenient but sensitive to hydration). All are less accessible than a tape.
For fat distribution rather than total percentage, use the waist-to-hip ratio calculator. For the simpler height-and-weight screen, use BMI — the BMI guide explains how the two complement each other. To set an energy target, use the calorie calculator.
Frequently asked questions
- How accurate is the tape-measure method?
- Usually within about 3 percentage points of a DEXA scan for an average build. It's less reliable for very lean or very muscular people.
- Why does the formula ask for hip measurement only for women?
- The US Navy method uses a separate equation per sex to reflect typical fat-distribution differences. The female equation includes hip circumference; the male one doesn't.
- Where exactly do I measure?
- Neck just below the larynx; waist at the navel (men) or narrowest point (women); hip at the widest point of the buttocks (women). Tape level, snug, not compressing.
- Why did my result change a lot between two attempts?
- The method is sensitive to measurement error — about 1–2 percentage points per centimetre on the waist. Measure each site twice and average, at the same time of day.
- What's a healthy body fat percentage?
- Broadly, 10–20% for men and 18–28% for women covers "fitness" to "acceptable" ranges. Essential fat (the minimum for normal function) is about 2–5% for men and 10–13% for women.
- Is this better than BMI?
- For the question "how much of me is fat," yes — BMI can't tell fat from muscle. For a fast population screen, BMI is simpler. They answer different questions.