How to use
- 1Choose a method: US Navy (tape measure) or Jackson-Pollock 3- or 7-site (calipers).
- 2Pick sex and units (cm/kg or in/lb).
- 3Enter the measurements shown; skinfolds are always in millimetres.
- 4Read your body fat, ACE category and — if you entered weight — fat mass and lean mass.
The US Navy method
Developed by Hodgdon and Beckett for the US Navy in 1984, this method uses height, neck and waist (plus hips for women). Men measure the waist at the navel, women at the narrowest point; hips at the widest point and the neck just below the larynx. Measuring in the morning, before eating, with the same tape improves consistency. Expect an error of roughly ±3–4 percentage points.
Jackson-Pollock 3-site and 7-site calipers
The Jackson-Pollock equations (men 1978, women 1980) estimate body density from the sum of skinfolds and age; the tool converts density to body fat with the Siri equation (fat % = 495 ÷ density − 450). The 3-site test uses chest, abdomen and thigh for men, and triceps, suprailiac and thigh for women. The 7-site test adds midaxillary, subscapular and the remaining sites. Take each fold on the right side two or three times and average them.
ACE body fat categories
The American Council on Exercise classifies men at 2–5 % essential fat, 6–13 % athletes, 14–17 % fitness, 18–24 % average and 25 %+ obese; women at 10–13 % essential fat, 14–20 % athletes, 21–24 % fitness, 25–31 % average and 32 %+ obese. Results are estimates, not a diagnosis — talk to a doctor or registered dietitian about weight and health goals.
Frequently asked questions
How can I measure body fat at home?
The easiest way is the US Navy method: measure height, neck and waist (and hips for women) with a tape and enter them. With calipers, the Jackson-Pollock 3-site test can be more precise.
What is a healthy body fat percentage for men?
ACE puts 14–17 % in the fitness range and 6–13 % in the athletic range; 25 % and above is classed as obese.
What is a normal body fat percentage for women?
25–31 % is average, 21–24 % fitness and 14–20 % athletic. Essential fat is naturally higher in women (10–13 %).
How accurate is the Navy body fat formula?
Compared with DEXA it is usually within about 3–4 percentage points. It is most useful for tracking change with repeated measurements under the same conditions.
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