Body Fat Calculator (US Navy Method)

This body fat calculator estimates your body fat percentage from simple tape measurements using the US Navy circumference method — the formula the American military uses for fitness assessments because it needs no calipers, scales or lab equipment. Men enter height, neck and waist circumference; women additionally enter hip circumference, since the female formula accounts for a different fat distribution. Everything is computed instantly in your browser and nothing you type is sent anywhere.

The method works on logarithms of your measurements: for men the formula is 495 / (1.0324 − 0.19077·log10(waist − neck) + 0.15456·log10(height)) − 450, and for women 495 / (1.29579 − 0.35004·log10(waist + hip − neck) + 0.22100·log10(height)) − 450, with all lengths in centimeters. Measure the waist at the navel for men and at the narrowest point for women, the neck just below the larynx, and the hips at their widest point — consistent measuring technique matters more than any formula detail.

The raw percentage is interpreted on the widely used ACE (American Council on Exercise) scale: essential fat (2–5% for men, 10–13% for women), athletes (6–13% / 14–20%), fitness (14–17% / 21–24%), average (18–24% / 25–31%) and obese (25%+ / 32%+). If you also enter your weight, the calculator splits it into fat mass and lean mass in kilograms — a more useful pair of numbers than weight alone when you are tracking a cut or a bulk, because it shows what kind of mass you are actually losing or gaining.

Like every circumference-based estimate, the US Navy method has a margin of error of roughly ±3–4% compared with DEXA scans — hydration, muscularity and where your body stores fat all shift the result. Use it to track your trend with consistent measurements rather than to judge a single reading, and remember this tool is not medical advice: for clinical body-composition assessment, talk to a healthcare professional.