Body Fat Calculator
Estimate your body fat percentage with a tape measure, skinfold calipers, or just your height and weight. Use more than one method to see how much they agree, then see how your number compares with CDC body scans of US adults.
Calculate your body fat
Three published methods: tape measure, skinfold calipers, or just height and weight. Results are compared with CDC body scans of US adults.
Uses only your height, weight, age and sex (Deurenberg formula). Quickest, but the least specific of the three.
Body fat percentage can be estimated three ways at home: the tape-measure (Navy) method uses your neck, waist and, for women, hips; the Jackson–Pollock method uses three skinfold measurements; the Deurenberg formula uses only BMI, age and sex. All three are estimates. The gold standard used by CDC is a DXA body scan, and our results compare your number with those scans.
Equations: US Army sample calculations, Jackson–Pollock and Siri, Deurenberg et al., 1991. Comparison data: our body fat percentage chart.
The tape-measure (Navy) method
Developed by Hodgdon and Beckett at the Naval Health Research Center in 1984, this method predicts body fat from neck and waist circumferences and height, plus hips for women. The same equations appear in the US Army’s sample calculations. Measurements go into the equations in inches; plugging centimeters into these constants gives badly wrong results, so the calculator converts for you.
Men: 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76
Women: 163.205 × log10(waist + hips − neck) − 97.684 × log10(height) − 78.387
Worked examples from the Army document: a woman with a 15-inch neck, 42-inch waist, 44-inch hips and 64-inch height, and a man with a 16-inch neck, 49-inch waist and 69-inch height. The document works them by hand with logarithms rounded to two or three decimals, getting 46.73% and 38.62%, and reports 47% and 39%. Computed exactly, they are 47.3% and 38.6%, which round to the same 47% and 39%.
The skinfold method (Jackson–Pollock 3-site)
Calipers measure the thickness of a pinch of skin and fat at three sites: chest, abdomen and thigh for men; triceps, suprailiac (just above the hip bone) and thigh for women. Jackson and Pollock’s equations turn the sum and your age into body density, and Siri’s equation converts density to body fat.
Men: density = 1.10938 − 0.0008267·S + 0.0000016·S² − 0.0002574·age
Women: density = 1.0994921 − 0.0009929·S + 0.0000023·S² − 0.0001392·age
Body fat % = 495 ÷ density − 450 (Siri)
S = sum of the three skinfolds in millimeters. One published reproduction prints the women’s age term as 0.0001395 rather than 0.0001392; the difference changes the result by less than 0.1 point even at age 60. Source: Serra et al., ConScientiae Saúde 2009, citing Jackson & Pollock 1978, Jackson, Pollock & Ward 1980 and Siri 1956.
The height-and-weight method (Deurenberg)
Deurenberg and colleagues measured body fat by underwater weighing in 1,229 people and fitted a formula for adults: body fat % = 1.20 × BMI + 0.23 × age − 10.8 × sex − 5.4, with sex = 1 for men and 0 for women. Its standard error is 4.1 points, and the authors found it slightly overestimates body fat in people with obesity (Deurenberg et al., Br J Nutr 1991). It needs no tape, but because it starts from BMI it inherits BMI’s blind spot: it can’t tell muscle from fat.
Which method is most accurate?
None of the three is a measurement; all are predictions. CDC calls DXA the most widely accepted method of measuring body composition, which is why we compare your result with DXA scans rather than with a fitness chart (CDC NHANES documentation). Deurenberg’s team reported that their BMI formula’s error is comparable to skinfold or bioelectrical impedance methods. Careful, repeated measurements help, and running two methods shows the range your true value is likely in.
What your result means
The calculator shows where your number sits against two references: the provisional healthy ranges matched to BMI cut-offs (Gallagher et al., 2000; for example 21–32.9% for women and 8–19.9% for men aged 20–39), and what US adults your age actually measure on CDC’s DXA scans. The full percentiles, by age and sex, are on our body fat percentage chart. To compare your weight rather than your fat, see average weight by height.
FAQ
How do I calculate my body fat percentage at home?
With a soft tape measure (neck, waist and, for women, hips) using the Navy equations; with skinfold calipers using the Jackson–Pollock equations; or from your BMI, age and sex using the Deurenberg formula. The calculator above does all three.
Can I calculate body fat from BMI?
Yes, approximately. Deurenberg’s formula predicts body fat from BMI, age and sex with a standard error of 4.1 points, but it can’t distinguish muscle from fat.
Why does my smart scale give a different number?
Scales, calipers, tape equations and DXA scans all measure different things and carry their own errors, so readings can differ by several points. Track one method over time rather than comparing across methods; our guide to how to measure body fat compares each method with DXA scans.
Does the Navy method work in centimeters?
The published constants assume inches. Entering centimeters directly into the inch equations gives a very wrong answer; the calculator converts metric measurements to inches first.
What is a healthy body fat percentage?
Provisional ranges matched to a healthy BMI are 8–19.9% for men and 21–32.9% for women aged 20–39, rising slightly with age (Gallagher et al., 2000). See the body fat percentage chart for every age group.
Sources
- US Army sample body fat calculations (Table B-5), reproduced in the study protocol NCT02734238, ClinicalTrials.gov. Equations from Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy men and women from body circumferences and height. Naval Health Research Center reports 84-11 and 84-29, 1984.
- Jackson AS, Pollock ML. Br J Nutr 1978;40:497–504; Jackson AS, Pollock ML, Ward A. Med Sci Sports Exerc 1980;12:175–81; Siri WE 1956 — as reproduced in Serra AJ, et al. ConScientiae Saúde 2009;8(1):19–24.
- Deurenberg P, Weststrate JA, Seidell JC. Body mass index as a measure of body fatness: age- and sex-specific prediction formulas. Br J Nutr 1991;65:105–14.
- Gallagher D, et al. Healthy percentage body fat ranges. Am J Clin Nutr 2000;72:694–701.
- National Center for Health Statistics. NHANES DXA whole body data, 2011–2018 (comparison percentiles: our calculation).
This calculator gives estimates for information. It is not a medical test or medical advice.