Body fat calculator (U.S. Navy method)
All you need is a tape measure. Enter your height and a few circumference measurements to estimate your body-fat percentage, plus your lean and fat mass if you add your bodyweight.
Gymex tracks your weight, 13+ body measurements and progress photos in the same app as your training.
Get the appHow the U.S. Navy method works
The U.S. Navy formula estimates body fat from circumference measurements, because fat around the waist (and hips, for women) rises as body fat rises, while neck size mostly tracks frame and muscle. It was developed for military fitness screening and is a practical home estimate. Studies typically find it within a few percentage points of lab methods for most people, though it is less accurate at very low or very high body fat.
How to measure
- Neck: just below the larynx (Adam’s apple), tape sloping slightly down at the front.
- Waist: men at the navel. Women at the narrowest point of the waist. Measure relaxed, after breathing out normally.
- Hips (women): around the widest part of the buttocks.
- Keep the tape snug but not compressing the skin. Measure at the same time of day, ideally in the morning.
Use the trend, not one reading
Any body-fat estimate has error, but measuring the same way every 2–4 weeks shows the direction clearly. Pair it with bodyweight and progress photos. If your weight is stable while your waist shrinks and your lifts go up, you’re recomposing. To set calories for your goal, use our TDEE and macro calculator.
Body-fat estimates are not a measure of health on their own. If you are under 18, pregnant, or have a medical condition, talk to a GP before acting on them.
Frequently asked questions
How accurate is the U.S. Navy body fat calculator?
For most adults it is usually within a few percentage points of lab methods such as DEXA. It is less accurate for very lean or very muscular people, so tracking the trend over time is more useful than any single reading.
Where should I measure my waist for the Navy method?
Men measure at the navel. Women measure at the narrowest part of the waist, plus the hips at their widest point. Measure relaxed after a normal breath out.
What is a healthy body fat percentage?
Ranges differ by age and sex. Many guidelines put roughly 10–20% for men and 18–30% for women in a healthy range. Very low body fat is not automatically healthier.
Can I use inches?
Yes. Switch units to inches and the calculator converts your measurements before applying the formula.
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These calculators give estimates for healthy adults. They are not medical advice. If you have an injury or a health condition, speak to a qualified professional before changing your training or diet.