Estimate your body fat percentage from tape measurements and from BMI.
The US Navy method uses height, neck and waist (plus hips for women). A 30-year-old man 178 cm tall with a 38 cm neck and 90 cm waist has about 20.1% body fat.
Body fat percentage is the share of your weight that is fat. This calculator gives two estimates: the US Navy circumference method — which uses neck, waist and, for women, hip measurements with your height — and the BMI method, which uses BMI, age and sex. It also shows your fat mass, lean mass and which fitness category your result falls into.
Both are estimates; DEXA scans, skinfold tests and bioimpedance scales are more precise. Measure the same way each time to track change, and compare with your BMI and lean body mass. The Army Body Fat Calculator uses a similar tape method with military standards.
The calculator applies the standard published formulas step by step.
| Item | Value |
|---|---|
| Body fat — US Navy method | 20.1% |
| Body fat — BMI method | 21% |
| Category (American Council on Exercise ranges) | Average |
| Fat mass (Navy) | 16.1 kg (35.5 lb) |
| Lean mass (Navy) | 63.9 kg (140.8 lb) |
| BMI | 25.2 kg/m² |
| Category | Women | Men |
|---|---|---|
| Essential fat | 10–13% | 2–5% |
| Athletes | 14–20% | 6–13% |
| Fitness | 21–24% | 14–17% |
| Average | 25–31% | 18–24% |
| Obese | 32% and over | 25% and over |
| Case | Body fat |
|---|---|
| Waist 80 cm | 12.4% |
| Waist 90 cm | 20.1% |
| Waist 100 cm | 26.7% |
| Waist 110 cm | 32.5% |
| Neck 42 cm, waist 90 cm | 17.2% |
Roughly 14–24% for women and 6–17% for men covers athletic to fit levels; 25–31% (women) and 18–24% (men) is an average range. Needs vary with age.
Neck: just below the larynx, tape sloping slightly down. Waist: at the navel for men, at the narrowest point for women. Hips: widest point. Don't pull the tape tight.
Typically within about 3–4 percentage points of laboratory methods for most people, but less accurate for very lean or very obese people.
They use different inputs. The BMI method ignores body shape; the tape method captures fat distribution. Treat both as ranges.
The minimum fat needed for normal body function — about 2–5% in men and 10–13% in women. Going below it is unsafe.
Gradual changes — more activity, strength training, adequate protein and a modest calorie deficit — work better than crash diets. Talk to a professional first.
It uses the published formula: Navy (men) = 495 ÷ (1.0324 − 0.19077·log(waist − neck) + 0.15456·log(height)) − 450 The full method and a worked example are shown on this page.
No. The calculator gives general estimates for information and education. It cannot diagnose or treat anything, so please speak to a doctor or qualified professional about your own health.
Yes. Choose centimetres or feet and inches for height, and kilograms, pounds or stone for weight; the results are converted for you.
No. Everything is calculated in your browser and nothing you enter is uploaded or saved.
