Body fat calculator
With a tape measure (US Navy method) or a skinfold caliper (Jackson-Pollock 3 or 7 sites): body fat percentage, category, fat mass and lean mass update as you type. Free, no sign-up.
With a tape measure: height, neck, waist and, for women, hips.
Just below the Adam's apple.
Men: at the navel. Women: at the narrowest point.
Result
- Body fat
- Category
- Fat mass
- Lean mass
To see the result, enter: sex, age, weight, height, neck, and waist.
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Create a free accountFind a professionalHow it's calculated
US Navy method
It uses height and the neck and waist circumferences, plus hips for women, with Hodgdon and Beckett's equations for the US Navy (Naval Health Research Center, 1984). Measurements are in centimeters and log is the base-10 logarithm.
- Men: % = 495 ÷ (1.0324 − 0.19077 × log(waist − neck) + 0.15456 × log(height)) − 450
- Women: % = 495 ÷ (1.29579 − 0.35004 × log(waist + hips − neck) + 0.22100 × log(height)) − 450
Jackson-Pollock skinfolds
The sum of the skinfolds (S, in millimeters) and age give body density (D), with the equations of Jackson and Pollock (1978) for men and Jackson, Pollock and Ward (1980) for women. The Siri equation (1961) turns density into body fat percentage.
- 7 sites, men: D = 1.112 − 0.00043499 × S + 0.00000055 × S² − 0.00028826 × age
- 7 sites, women: D = 1.097 − 0.00046971 × S + 0.00000056 × S² − 0.00012828 × age
- 3 sites, men (chest, abdominal, thigh): D = 1.10938 − 0.0008267 × S + 0.0000016 × S² − 0.0002574 × age
- 3 sites, women (triceps, suprailiac, thigh): D = 1.0994921 − 0.0009929 × S + 0.0000023 × S² − 0.0001392 × age
- Body fat % = (4.95 ÷ D − 4.5) × 100
Category, fat mass and lean mass
The category follows the American Council on Exercise at the lean end (athlete, fitness) and, from there up, the cut-offs of Gallagher and colleagues (2000) for sex and age. Fat mass and lean mass come from body weight:
- Fat mass = weight × body fat % ÷ 100
- Lean mass = weight − fat mass
Limits
These are estimates for adults and don't replace an assessment by a professional. The result depends a lot on who measures and where: always measure on the right side of the body, at least twice at each site, and use the average.
Frequently asked questions
Which method should I use?
None of them is exact; it depends on what you have to hand. The 7 skinfolds cover more of the body and are the most complete; the 3 skinfolds are quicker and give very close numbers. The US Navy method only needs a tape measure and is the easiest to repeat, but since it relies on circumferences alone, it's further off for very muscular people.
What body fat percentage is healthy?
It depends on sex and age. For adults aged 20 to 39, Gallagher and colleagues (2000) put overweight from 20% in men and 33% in women, and obesity from 25% and 39%. The cut-offs rise with age.
Why does the calculator ask for age?
The Jackson-Pollock equations use age to work out body density, and the cut-offs for each category change with age. With the US Navy method, age only counts for the category.
What is lean mass?
Everything that isn't fat: muscle, bone, organs and water. It's your weight minus your fat mass, and fat mass is your weight times your body fat percentage. When losing weight, the goal is usually to lose fat mass and keep lean mass.