Body Fat Calculator
Estimate your body fat percentage from a few tape-measure readings.
Good to know. Two people with the same BMI can have very different body fat. A tape measure tells them apart.
Not medical advice. A general estimate for healthy adults.
How it works
In plain words
The US Navy method estimates body fat from circumferences, which track fat better than weight does. It uses the logarithm of the waist minus the neck (plus the hips for women) and of the height, in centimetres.
The formula
men: 495 ÷ (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450 women: 495 ÷ (1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.221 × log₁₀(height)) − 450
Worked example
A man 178 cm tall with a 38 cm neck and an 85 cm waist: 495 ÷ (1.0324 − 0.19077 × log₁₀(47) + 0.15456 × log₁₀(178)) − 450 = 16.4%, in the fitness range.
Sources
- Hodgdon and Beckett, Prediction of percent body fat for US Navy men and women from body circumferences and height, Naval Health Research Center, 1984 The circumference equations.
- American Council on Exercise, body fat percentage norms Essential fat, athletes, fitness, average and obese ranges.
Sources checked September 30, 2026. 5 automated tests check its answers on every change.
About the body fat calculator
Body fat percentage tells you how much of your weight is fat, rather than muscle, bone and water. It says more about health and fitness than weight or BMI, which can’t tell a muscular person from someone carrying extra fat.
This calculator uses the US Navy method, developed by Hodgdon and Beckett in 1984 and still used by the US military. It needs only a tape measure: height, neck and waist, plus hips for women. Measure on bare skin, with the tape snug but not pressing in, and breathe out normally before measuring the waist. For men, measure the waist at the navel; for women, at the narrowest point, and the hips at the widest.
Compared with lab methods such as DEXA scans, the Navy formula is usually within 3 to 4 percentage points for most people. It is less accurate for very lean or very muscular builds and for older adults. Take measurements the same way each time, and treat changes over weeks as more meaningful than a single reading.
The categories come from the American Council on Exercise. Women naturally carry more essential fat than men, so the ranges are higher: an average range of 25 to 31% for women compares with 18 to 24% for men. Very low body fat is not healthier; essential fat is needed for hormones and organs.
Questions people ask
What is a healthy body fat percentage?
For men roughly 14 to 24%, and for women roughly 21 to 31%, covering the fitness and average categories of the American Council on Exercise.
How accurate is the Navy method?
Usually within 3 to 4 percentage points of lab methods, if you measure carefully. It is less accurate for very muscular or very lean people.
Where do I measure my waist?
Men at the navel, women at the narrowest point of the waist. Measure after breathing out normally, without pulling the tape tight.