U.S. Navy: body fat from log-transformed neck, waist (and hip for women) plus height. Jackson-Pollock: three skinfolds give body density via a quadratic, converted to fat percentage with the Siri equation (495 ÷ density − 450).
Hodgdon & Beckett (1984) Naval Health Research Center; Jackson & Pollock (1978, 1980); Siri (1961).
±3–4% versus hydrostatic weighing for both methods when measured carefully. Technique is the dominant source of error, so measure the same way each time.
Pregnant women, and cases where measurement sites are hard to locate reliably. For clinical precision, use DEXA or hydrostatic weighing.
Frequently asked questions
The U.S. Navy tape method lands within about 3–4% of a lab measurement when you measure carefully, and Jackson-Pollock skinfolds within about 3.5% with a trained tester. Both are far more useful than BMI, but neither replaces a DEXA scan.
The Navy method needs only a tape measure and is easy to repeat at home. Skinfolds can be more accurate but require calipers and good technique. Pick whichever you can measure consistently — consistency matters more than the method.
Measure your neck below the larynx, and your waist at the navel (men) or at the narrowest point (women). Women also measure the hips at their widest. Keep the tape snug and level, and don't pull it tight.
For men: chest, abdomen, and thigh. For women: triceps, suprailiac (just above the hip bone), and thigh. Add the three measurements in millimetres and enter the total.
Rough guides: men are athletic around 6–13%, fit at 14–17%, and average at 18–24%; women run about 10 points higher at each stage because of essential fat. Very low body fat carries its own health risks.
Hydration, measurement technique, and time of day all shift the result by a percent or two. Measure under the same conditions each time and watch the trend rather than any single reading.