Estimate your body fat percentage with a tape measure using the U.S. Navy method, and see your fat mass, lean mass and body fat category.
How the U.S. Navy method works
The U.S. Navy developed a simple way to estimate body fat from a few tape measurements. It uses height, neck and waist for men, and adds hips for women. Studies show it is usually within a few percentage points of lab methods for many people, which makes it a practical way to track change over time.
Men: %BF = 495 ÷ (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450
Women: %BF = 495 ÷ (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.221 × log10(height)) − 450
Measurements are in centimeters in these formulas; the calculator converts inches automatically.
How to measure
- Neck: just below the larynx (Adam's apple), tape sloping slightly down at the front.
- Waist (men): horizontally at the level of the navel.
- Waist (women): at the narrowest point of the abdomen.
- Hips (women): around the widest part of the buttocks.
Measure on bare skin, relaxed, without pulling the tape tight. Take each measurement twice.
Worked example
A man who is 70 in tall with a 15 in neck and 34 in waist has an estimated body fat of about 17.4%. At 185 lb, that is about 32 lb of fat and 153 lb of lean mass. A woman who is 65 in tall with a 13 in neck, 30 in waist and 39 in hips comes out at about 29.5%.
Body fat categories
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletic | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Above average | 25%+ | 32%+ |
Categories as commonly published by the American Council on Exercise.
Frequently asked questions
Is this more useful than BMI?
It adds information that BMI misses, because it estimates fat rather than total weight. Using both together gives a fuller picture.
How often should I measure?
Every two to four weeks is enough to see real trends.
Related tools
These calculators give estimates for healthy adults based on published formulas. They are not medical advice. Talk to a doctor or registered dietitian before making major changes to your diet or exercise, especially if you are pregnant, under 18 or have a health condition.