Quick answer: The U.S. Navy method estimates body fat from tape measurements. For men it uses height, neck and waist, and for women it adds the hips. A man who is 178 cm tall with a 38 cm neck and a 90 cm waist has an estimated body fat of about 20.1%.
Body fat percentage says more about your body composition than weight or BMI alone. Two people with the same weight can have very different amounts of fat and muscle. Precise measurement needs a DEXA scan or similar equipment, but the US Navy method gives a useful estimate using nothing more than a tape measure.
The method uses circumferences rather than weight, so it picks up changes in your waist as you lose fat or build muscle. For the best results, measure in the morning, keep the tape snug but not tight, and take each measurement two or three times.
The Navy formula
The formula was developed for the US Navy to check whether personnel met body composition standards. It uses the logarithm of body measurements in centimeters:
Women: 495 ÷ (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450
The result is grouped using the American Council on Exercise ranges. For men: essential fat 2 to 5%, athletes 6 to 13%, fitness 14 to 17%, average 18 to 24%, and 25% and above is above average. For women the same groups are 10 to 13%, 14 to 20%, 21 to 24%, 25 to 31%, and 32% and above.
A worked example
Example. A man who is 178 cm tall with a 38 cm neck and 90 cm waist gets an estimated body fat of 20.1%. At 80 kg that is about 16.1 kg of fat and 63.9 kg of lean mass.
Typical body fat ranges
| Category | Women | Men |
|---|---|---|
| Essential fat | 10 to 13% | 2 to 5% |
| Athletes | 14 to 20% | 6 to 13% |
| Fitness | 21 to 24% | 14 to 17% |
| Acceptable | 25 to 31% | 18 to 24% |
| Obesity | 32% and above | 25% and above |
Commonly used ranges from the American Council on Exercise. Healthy ranges also depend on age, and no single range fits everyone.
Common mistakes to avoid
- Measuring the waist at the wrong place. For men it is at the navel and for women at the narrowest point, with a relaxed stomach and the tape level.
- Pulling the tape tight or measuring over clothes. Small errors of a centimeter change the result by a full percentage point or more.
- Comparing the estimate with a scan or scale. Methods differ by several points, so use one method and track the trend over time.
Go deeper: read our guide BMI Explained: Categories, Limits and Alternatives.
Frequently asked questions
How accurate is the Navy method?
It is an estimate. Compared with DEXA scans, it can be off by several percentage points for some people. It is most useful for tracking your own change over time, if you measure the same way each time.
Where exactly should I measure my waist?
For men, measure at the level of the navel. For women, measure at the narrowest part of the waist, or at the navel if there is no clear narrowing. Stand relaxed and measure after breathing out normally.
Why are the categories different for men and women?
Women naturally carry more essential body fat than men, which supports hormonal and reproductive health, so healthy ranges are higher.
Can I lower my body fat and keep my muscle?
Most people can, with a moderate calorie deficit, enough protein and resistance training. Very fast weight loss tends to cost more muscle.
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Sources and further reading
- 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, 1984
- Body fat percentage (Wikipedia)
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