Body Fat Calculator: US Navy Method
This body fat calculator estimates your body fat percentage with nothing more than a tape measure. It uses the US Navy method, which works from your height and the size of your neck, waist and, for women, hips. Add your weight to see how much of it is fat and how much is lean mass.
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Quick answer: A man who is 170 cm tall with a 38 cm neck and an 85 cm waist has about 18% body fat by the US Navy method, at the top of the fitness range. Healthy ranges are roughly 14 to 24% for men and 21 to 31% for women.
How to use the body fat calculator
- Choose your sex and units, then enter your height and weight.
- Measure your neck just below the Adam’s apple, with the tape sloping slightly down at the front.
- Measure your waist: men at the navel, women at the narrowest point. Stand relaxed and do not pull your stomach in.
- Women also measure the hips at the widest point of the buttocks.
- Read your body fat percentage, category and fat and lean mass.
Body fat percentage chart
| 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% |
| Average | 25 to 31% | 18 to 24% |
| Obese | 32% and above | 25% and above |
Source: American Council on Exercise. Healthy ranges rise a little with age.
The US Navy formula
For men, body fat % = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76. For women, body fat % = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387, with all measurements in inches. The formula was built from underwater weighing data and is used by the US military for fitness checks.
Body fat vs BMI
BMI only uses height and weight, so a muscular person can score as overweight. Body fat percentage looks at what the weight is made of, which says more about health and fitness. Waist size on its own is also a useful sign: health risks rise when a man’s waist is over 102 cm (40 in) or a woman’s is over 88 cm (35 in).
Other ways to measure body fat include skinfold calipers, smart scales (bioimpedance) and DEXA scans, which are the most accurate. All home methods are estimates, and this tool is not medical advice. Compare with your BMI, find a target with the ideal weight calculator, or plan meals with the calorie calculator.
FAQ
How accurate is the Navy method?
It is usually within 3 to 4 percentage points of a lab test for most people, but less accurate for very lean or very muscular builds.
How often should I measure?
Every two to four weeks is enough to see a trend. Daily changes are mostly water.