Health / Body
Body Fat Calculator (US Navy Method)
Estimate your body fat percentage from a tape measure, with the US Navy method: height, neck, and waist, plus hips for women, in centimetres or inches, with the American Council on Exercise categories.
Body Fat Calculator (US Navy Method): The US Navy method, from Hodgdon and Beckett's 1984 study and used by the US Department of Defense, estimates body fat from circumferences. For men it is 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76, in inches; for women 163.205 × log₁₀(waist + hips − neck) − 97.684 × log₁₀(height) − 78.387. Centimetres are converted to inches first. Runs 100% locally in your browser with zero server file uploads.
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| Essential fat | 2–5% |
|---|---|
| Athletes | 6–13% |
| Fitness | 14–17% |
| Average | 18–24% |
| Obese | 25%+ |
Measure with a soft tape, snug but not pressing into the skin, and take the average of three readings. Men measure the waist across the navel; women at the narrowest point, and the hips at the widest. The Navy method is usually within 3 to 4 percentage points of a laboratory measurement; it is a guide, not a diagnosis.
Worked examples
A man 70 in tall with a 15 in neck and a 34 in waist: 86.010 × log₁₀(19) − 70.041 × log₁₀(70) + 36.76 = 17.5%, in the fitness range. A woman 64 in tall with a 13 in neck, 29 in waist, and 38 in hips: 27.9%, in the average range.
For a measure that needs only height and weight, use the BMI calculator; to plan what to eat, the calorie calculator.
Getting consistent readings
Measure in the morning before eating, standing relaxed, with the tape level and snug but not compressing the skin. Breathe out normally before the waist reading, without pulling the stomach in.
Small day-to-day changes are mostly water and measuring error. Compare readings a few weeks apart, taken the same way, to see the trend.
How to use it
- Choose male or female, and centimetres or inches.
- Measure height, neck, and waist (and hips for women) with a soft tape.
- Read your body fat percentage and its category; add your weight to see fat and lean mass.
Privacy & limitations
Your measurements are worked out in your browser and never sent anywhere.
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Frequently asked questions
How accurate is the Navy method?
It is usually within 3 to 4 percentage points of a laboratory measurement, and it is most useful for following your own trend with the same tape and the same routine.
Where exactly should I measure?
The neck just below the larynx, sloping slightly down at the front; men's waist across the navel; women's waist at its narrowest and hips at the widest point of the buttocks.
What is a healthy body fat percentage?
The American Council on Exercise puts average at 18–24% for men and 25–31% for women, and fitness ranges lower; health also depends on where fat sits, which the waist measurement partly reflects.
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