Body Fat Calculator

A formula developed by Navy researchers (Hodgdon & Beckett, 1984) that estimates body fat percentage from a few tape-measure circumferences plus height. It needs neck and waist for men, and neck, waist, and hip for women. It correlates well with hydrostatic weighing — typically within ±3–4% body fat for adults with typical fat distribution.

Good — but it's still an estimate. The Navy method assumes you store fat in roughly average locations. Very muscular men with thick necks or very lean people with low-volume waists can get readings several percentage points off. For precise measurement, DEXA, hydrostatic weighing, or BodPod are the gold standards.

Use a flexible cloth tape, snug but not compressing the skin, and keep the tape level all the way around. Neck: just below the larynx. Waist (men): at the navel. Waist (women): at the narrowest point. Hip (women): at the widest point. Measure first thing in the morning before eating for the most consistent readings, and average two measurements.

American Council on Exercise scale — men: essential fat <6%, athletes 6–13%, fitness 14–17%, average 18–24%, above average ≥25%. Women: essential fat <14%, athletes 14–20%, fitness 21–24%, average 25–31%, above average ≥32%. Higher essential ranges in women reflect reproductive physiology. The right range for any one person depends on age, training level, and goals.

The Navy formula was fit separately for men and women. The men's equation uses just waist − neck, while the women's equation uses waist + hip − neck because women's body fat distributes differently and the hip circumference adds predictive power. Without it, the women's formula loses accuracy.