Body Fat Calculator

The U.S. Navy method estimates body fat from circumference measurements rather than calipers. For men it uses height, neck, and waist; for women it adds the hip. The measurements feed a logarithmic formula validated against hydrostatic weighing, giving a result within about 3–4% of lab methods for most people.

Measure the neck just below the larynx (Adam's apple) with the tape sloping slightly downward to the front. Measure the waist at the navel for men and at the narrowest point for women. Measure the hips at the widest point of the buttocks. Keep the tape snug but not compressing the skin, and measure on bare skin after exhaling.

The American Council on Exercise lists these ranges. Men: essential 2–5%, athletes 6–13%, fitness 14–17%, average 18–24%, obese 25%+. Women: essential 10–13%, athletes 14–20%, fitness 21–24%, average 25–31%, obese 32%+. Women naturally carry more essential fat than men.

It is a quick, equipment-free estimate that correlates reasonably well with more precise methods like DEXA scans and hydrostatic weighing, typically within 3–4%. Accuracy drops for very lean or very heavy individuals. For tracking trends over time it is reliable as long as you measure consistently.

Men: %fat = 495 / (1.0324 − 0.19077·log10(waist − neck) + 0.15456·log10(height)) − 450, using inches. Women: %fat = 495 / (1.29579 − 0.35004·log10(waist + hip − neck) + 0.22100·log10(height)) − 450. The women's formula adds the hip measurement because fat distribution differs by sex.