A walkthrough, end to end.
- 1
Measure your neck just below the larynx with a soft tape, snug but not compressing skin. Read the number to the nearest 0.5 cm or quarter-inch.
- 2
Measure your waist at the level of your navel, breathing normally — not at the narrowest point and not while sucking in.
- 3
If you're female, measure your hip at its widest point with feet together. The Navy method uses hip circumference for women but not for men.
- 4
Enter the measurements, your height, weight and sex. The calculator returns your body fat percentage and shows where it falls on the ACE category scale.
US Navy circumference method
The Navy method estimates body fat by measuring how circumferences differ from height — fatter people have proportionally larger waists relative to height. Validated against hydrostatic weighing on hundreds of Navy personnel; accuracy is within ±3% for most adults.
What you can do with this.
Body fat calculator for men
Men only need three measurements: neck, waist, and height. The formula uses the difference between waist and neck — if you're carrying belly fat, that gap widens and the percentage rises.
Body fat calculator for women
Women add a hip measurement. The female version uses (waist + hip − neck) instead of (waist − neck) because women carry more lower-body fat on average. Measuring hip accurately matters — find the widest point and stand with feet together.
Body fat calculator without calipers
Calipers are notoriously hard to use accurately without practice — the inter-tester variability is huge. The Navy circumference method requires only a soft measuring tape and gives more consistent results for most people.
Tracking body fat changes during a cut
Measure once a week at the same time of day in the same conditions (morning, fasted, before training). Look for trend over 2–3 weeks; week-to-week noise from water and digestion is large.
Body fat vs BMI — which is more useful?
BMI is fast and uses scale weight. Body fat % is slower (you need a tape) but actually tells you about composition. A BMI 27 powerlifter at 14% body fat is in great shape; a BMI 27 desk worker at 30% body fat has very different metabolic risk.
Healthy body fat ranges (ACE)
American Council on Exercise: men — Essential 2–5%, Athlete 6–13%, Fitness 14–17%, Average 18–24%, Obese 25%+. Women — Essential 10–13%, Athlete 14–20%, Fitness 21–24%, Average 25–31%, Obese 32%+.
Body fat calculator 2026 — what's current
The US Navy circumference method is still the standard tape-based formula in 2026 — it was developed in the 1980s and continues to perform well against DEXA in validation studies. What's changed is wider availability of consumer body-composition scales and bioimpedance devices; those vary in accuracy, but the Navy formula remains the most reproducible no-equipment option.
Frequently asked.
Within ±3% for most adults — comparable to skinfold calipers in trained hands and much better than calipers in untrained hands. For precise numbers, DEXA scanning is the gold standard (±1.5%).
Neck: just below the larynx (Adam's apple), tape level all the way around. Waist: at navel level, breathing normally. Hip (women): widest point of hips/buttocks, feet together. Don't compress skin; tape should be snug but readable.
Women's body fat distributes more across hips and thighs. Including hip circumference accounts for that. Men's body fat is more abdominal on average, so waist alone (relative to neck and height) gives a better estimate.
It's reasonably accurate down to about 8% (men) and 16% (women). Below that the formula tends to overestimate. Same goes for bodybuilders during peak week — extreme glycogen depletion can skew the numbers up.
Different formula, similar inputs. The US Army formula uses log10(waist − neck) and log10(height) but with different constants — derived from a different reference dataset. The Navy method is more widely cited; the Army method is what military personnel are evaluated against under AR 600-9.
No. Every calculation runs in your browser. There's no server processing, no analytics on inputs, no cookies storing your numbers.