How to measure
Use a soft, non-stretch tape. Measure on bare skin, ideally in the morning before eating. Keep the tape level and snug without pressing into the skin, and take each measurement twice.
- Height: stand against a wall without shoes.
- Neck: just below the Adam's apple, with the tape sloping slightly downward at the front. Don't flare your neck.
- Waist (men): around the belly button, level with the floor. Breathe out normally and don't hold your stomach in.
- Waist (women): at the narrowest point, between the bottom of the ribs and the top of the hip bones.
- Hips (women): at the widest point of the hips and buttocks, feet together.
The US Navy formula
The method was developed by Hodgdon and Beckett at the US Naval Health Research Center in 1984 to estimate body fat from simple measurements. This calculator uses the metric equations, with logarithms in base 10, and converts inches to centimetres first.
Men: body fat % = 495 ÷ (1.0324 − 0.19077 × log(waist − neck) + 0.15456 × log(height)) − 450
Women: body fat % = 495 ÷ (1.29579 − 0.35004 × log(waist + hip − neck) + 0.22100 × log(height)) − 450
Worked examples
Man: 178 cm tall, 38 cm neck, 86 cm waistWaist minus neck is 48 cm. Putting the numbers in gives an estimated 17.2% body fat, in the Fitness category. At 80 kg that is about 13.8 kg of fat and 66.2 kg of lean mass.
Woman: 165 cm tall, 32 cm neck, 72 cm waist, 98 cm hipsWaist plus hips minus neck is 138 cm. The estimate is 27.4% body fat, in the Average category.
Body fat categories
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletes | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Obese | 25% and over | 32% and over |
These ranges come from the American Council on Exercise. They are general guides, not targets. Very low body fat is hard to sustain and can affect hormones and health, especially for women.
Using your result
- Better calorie estimates: send your result to the Katch-McArdle calculator, which works from lean mass.
- Tracking progress: re-measure every 2–4 weeks. If your weight is steady but your waist and body fat are falling, you are likely gaining muscle while losing fat.
- Choosing a goal: your body fat helps decide whether to cut or bulk next.
Not sure which TDEE formula your result should feed into? See which TDEE formula to use.
Related
Sources
- Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy men from body circumferences and height. Report No. 84-11. San Diego, CA: Naval Health Research Center; 1984.
- Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy women from body circumferences and height. Report No. 84-29. San Diego, CA: Naval Health Research Center; 1984.
- American Council on Exercise. Body fat percentage categories (essential fat, athletes, fitness, average, obese).
Frequently asked questions
How accurate is the US Navy body fat method?
It is a reasonable estimate for many people, but less precise than a DEXA scan. Accuracy depends a lot on careful measuring. It tends to be less reliable for very muscular people and for people whose fat is distributed in an unusual way. Use it to track change over time with the same method.
What is a healthy body fat percentage?
There is no single healthy number. The American Council on Exercise lists 14–24% as the fitness-to-average range for men and 21–31% for women. Essential fat, the minimum the body needs, is about 2–5% for men and 10–13% for women.
Why do women need hip measurements?
Women tend to store more fat around the hips and thighs, so the female equation includes the hip measurement to capture it. The male equation only uses neck and waist.
How often should I measure body fat?
Every 2–4 weeks is enough. Body fat changes slowly, and measuring more often mostly picks up noise from water, food and small differences in tape placement.
Can I use this result in the TDEE calculator?
Yes. Use the button under your result to open the Katch-McArdle calculator with your body fat already filled in. Katch-McArdle estimates BMR from lean mass, which can be more accurate if your body fat estimate is reliable.