Body fat calculator
Three estimates side by side: the U.S. Navy tape-measure method, the Jackson-Pollock three-site skinfold method if you have calipers, and a formula from BMI for when you have neither. Fill in what you have; each method shows up as soon as it has its inputs.
| Method | Body fat | Fat · lean (kg) |
|---|
Three methods, three kinds of error
U.S. Navy method. Developed by Hodgdon and Beckett at the Naval Health Research Center in 1984, it predicts body fat from height and circumferences: neck and waist for men, plus hips for women. It needs only a tape measure, and it is consistent if you measure the same way each time, which makes it good for tracking change. Measure the waist at the navel for men and at the narrowest point for women, relaxed, not sucking in.
Jackson-Pollock 3-site skinfolds. Calipers pinch a fold of skin and fat at three sites (chest, abdomen and thigh for men; triceps, above the hip bone and thigh for women). The sum predicts body density, and the Siri equation turns density into a body-fat percentage. Done by a practised tester it is one of the better field methods; done by yourself for the first time, readings can vary by several millimetres.
From BMI. Deurenberg and colleagues fitted body fat to BMI, age and sex in 1991. It is a population estimate: right on average, but it cannot tell a muscular person from a heavier one with the same BMI. Use it only when you have nothing else.
What the percentage is good for
Knowing your body fat lets the TDEE calculator add two lean-mass equations to its average and set protein on lean mass rather than total weight. For tracking, the trend matters more than the exact figure: use one method, measure under the same conditions every two to four weeks, and look at the direction.
Rough ranges
The American Council on Exercise chart is a common reference: essential fat about 2–5% for men and 10–13% for women; athletes 6–13% and 14–20%; fitness 14–17% and 21–24%; average 18–24% and 25–31%. Ranges for health depend on age and are best discussed with a clinician.