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Body Fat Calculator Without Measurements

Paul Hummel Last reviewed October 6, 2026 3 min read
Calculator

Estimate body fat without a tape

Formula by Deurenberg et al. (1991) from BMI, age and sex.

Estimated body fat
0%
BMI
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Fat mass
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Fat-free mass
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Estimate per Deurenberg et al. (1991). Standard error of estimate reported in the study: 4.1 percentage points.
Quick answer

Without a tape measure, body fat can be estimated from BMI, age and sex. The Deurenberg et al. (1991) formula has a standard error of estimate of 4.1 percentage points in adults.

Calculating body fat without measurements – how does it work?

Without a tape measure, calipers or a body fat scale, you can only estimate from data everyone knows: height, weight, age and sex. Deurenberg et al. (1991) developed a formula in adults that derives body fat percentage from BMI:

Body fat (%) = 1.20 × BMI + 0.23 × age − 10.8 × sex − 5.4
Sex: men = 1, women = 0.

How accurate is the estimate?

For adults, Deurenberg et al. (1991) report a standard error of estimate of 4.1 percentage points. The authors state that this error is comparable to that of other estimation methods. A result of 18% can therefore realistically be a few points higher or lower.

Limits of the BMI formula

BMI does not distinguish between muscle and fat. People with a lot of muscle mass have lower body fat at the same weight than the formula assumes. For lifters, the Navy method with a tape measure is usually the better choice because it includes waist and neck circumference.

The formula applies to adults. For children and adolescents, Deurenberg et al. (1991) gave a separate equation that this calculator does not use.

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Related questions

Sources

  1. Deurenberg, P., Weststrate, J. A. & Seidell, J. C. (1991). Body mass index as a measure of body fatness: age- and sex-specific prediction formulas. Br J Nutr, 65(2), 105–114. DOI
  2. Hodgdon, J. A. & Beckett, M. B. (1984). Prediction of Percent Body Fat for U.S. Navy Men from Body Circumferences and Height. Naval Health Research Center. DTIC
This content is for general informational purposes only and is not a substitute for medical or nutritional advice. Results from equations are estimates and may vary individually.