Short answer
The U.S. Navy method estimates body fat from circumferences. For a man, 495 ÷ (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450, in cm. A 90 cm waist, 38 cm neck and 178 cm height give 20.1%.
1. The formulas (centimetres)
Men: 495 ÷ (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450
Women: 495 ÷ (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450
If you measure in inches, multiply by 2.54 first. 35.4 in is 90 cm.
2. Where to measure
- 1Neck: just below the larynx.
- 2Waist: at the navel for men, at the narrowest point for women.
- 3Hips (women only): at the widest point.
- 4Height: without shoes.
Keep the tape snug without compressing the skin, and use the same spots every time.
3. Worked examples
| Person | Measurements | Result |
|---|---|---|
| Man | Waist 90, neck 38, height 178 | 20.1% |
| Same man | Waist 100 | 26.7% |
| Same man | Waist 85 | 16.4% |
| Woman | Waist 78, hips 100, neck 32, height 165 | 31.4% |
Ten centimetres on the waist moves the result by almost seven points, so measure carefully.
4. Limits
The Navy method is a field estimate. Its error varies between people, and it is less reliable for very muscular builds. Use it to track a trend with the same technique, not as a replacement for a clinical scan.
The Body Fat Calculator does the maths and shows your category, fat mass and lean mass. Next: healthy body fat percentage by age and sex.
5. Frequently asked questions
What is the Navy body fat formula?expand_more
A logarithmic equation using waist, neck and height (and hips for women) to estimate body fat.
Do I need hip measurements?expand_more
Only women. The women's formula includes the hips.
How accurate is the Navy method?expand_more
It is a field estimate with meaningful error, so use it for trends.
Can I use inches?expand_more
Convert to centimetres first by multiplying by 2.54, or use the calculator's unit toggle.