Body Fat Calculator
Estimate your body-fat percentage with the US Navy tape method, the BMI method or a 3- or 7-site skinfold test, and see your ACE category, fat and lean mass, the healthy range for your age and how much fat you would lose to reach a target.
How it works
US Navy, men: BF% = 495 ÷ (1.0324 − 0.19077·log₁₀(waist − neck) + 0.15456·log₁₀(height)) − 450 · women: BF% = 495 ÷ (1.29579 − 0.35004·log₁₀(waist + hip − neck) + 0.22100·log₁₀(height)) − 450 (all in cm) · BMI method: BF% = 1.20 × BMI + 0.23 × age − 16.2 (men) or − 5.4 (women) · skinfold: body density from the Jackson & Pollock 3- or 7-site equation, then BF% = 495 ÷ density − 450 (Siri) · fat mass = weight × BF%, lean mass = weight − fat mass
Pick the method that matches what you can measure. The US Navy tape method turns neck, waist and (for women) hip girths into a body-fat estimate and is usually within 3–4 percentage points of lab tests. The BMI method (Deurenberg) needs only height, weight, age and sex, but it cannot tell muscle from fat. The skinfold methods use caliper readings: the 3-site test uses chest, abdomen and thigh for men and triceps, suprailiac and thigh for women; the 7-site test adds midaxillary and subscapular folds and uses all seven for both sexes. The Jackson & Pollock equations give body density, which the Siri equation turns into a percentage. The result is rated against the American Council on Exercise categories and the age-based healthy ranges of Gallagher et al., and compared with the Jackson & Pollock ideal for your age. Fat and lean mass follow from your weight, and the weight at a target body fat assumes you keep your current lean mass.
Worked example
A 30-year-old man, 69 in tall (175.26 cm) and 170 lb, with a 15-in neck (38.1 cm) and a 34-in waist (86.36 cm): BF = 495 ÷ (1.0324 − 0.19077 × log₁₀(48.26) + 0.15456 × log₁₀(175.26)) − 450 ≈ 17.9%, at the top of the "Fitness" ACE category and inside the healthy 8–19% range for his age. Fat mass is about 30.4 lb and lean mass 139.6 lb. The Jackson & Pollock ideal at 30 is 12.7%, which at the same lean mass means a weight of about 159.9 lb, so about 10.1 lb of fat to lose. His BMI of 25.1 gives 20.8% with the BMI method, a little higher because BMI cannot see his build.
Sources: Hodgdon JA, Beckett MB (1984) — Prediction of percent body fat for U.S. Navy men and women from body circumferences and height · Jackson AS, Pollock ML (1978) — Generalized equations for predicting body density of men · Jackson AS, Pollock ML, Ward A (1980) — Generalized equations for predicting body density of women · Deurenberg P et al. (1991) — Body mass index as a measure of body fatness · Gallagher D et al. (2000) — Healthy percentage body fat ranges · American Council on Exercise — Percent body fat norms
Frequently asked questions
Which method is most accurate?
A 7-site skinfold test done by a trained person and the tape method are both usually within 3–4 percentage points of lab methods such as DEXA. The BMI method is the least precise because it cannot tell muscle from fat. Whichever you choose, use the same method each time to track change.
How do I take skinfold measurements?
Pinch a double fold of skin and fat between thumb and finger, place the caliper jaws about 1 cm away, wait two seconds and read the dial in millimeters. Measure on the right side, take each site 2–3 times and average the readings.
When should I measure?
Morning, before food and water, tape parallel to the floor. Consistency beats precision.
What body fat should I aim for?
For adults aged 20–39, roughly 8–19% for men and 21–32% for women is considered healthy, and the range rises a little with age. The "fitness" bands, about 14–17% for men and 21–24% for women, suit most people who train regularly. Going below the essential-fat level (about 2–5% for men and 10–13% for women) is unsafe.
How is "fat to lose" worked out?
The calculator keeps your current lean mass and finds the weight at which that lean mass makes up the rest of your body at the target percentage: weight = lean mass ÷ (1 − target). The difference from your current weight is the fat to lose. In practice some lean mass is often lost too, so eat enough protein and keep strength training.
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This is a general educational estimate, not medical advice. Bodies differ — for decisions about diet, training, medication or health conditions, talk to a doctor or registered dietitian.