How to use the Body Fat Calculator (US Navy Method)
- Choose your sex and whether you measure in centimetres or inches.
- Measure your height without shoes, your neck just below the larynx, and your waist. Men measure at the navel, women at the narrowest point.
- Women also measure the hips at the widest point.
- Read the estimate and the general category. Repeat the same measurements under the same conditions to track changes.
Formula used
Men: body fat % = 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. Measurements in centimetres.
Worked example
Here is the Body Fat Calculator (US Navy Method) worked through with the example values shown above, so you can check each step by hand.
| Inputs | |
|---|---|
| Sex | Male |
| Measurements in | Centimetres |
| Height | 178 |
| Neck (below the larynx) | 38 |
| Waist (at the navel for men, narrowest for women) | 90 |
| Hips (women only, widest point) | 95 |
| Result | |
| Estimated body fat | 20.15% |
| General category | Average |
Body fat at different waist sizes
For the default male profile in centimetres, changing only the waist.
| Waist (at the navel for men, narrowest for women) | Estimated body fat | General category |
|---|---|---|
| 75 | 7.88% | Athletic |
| 85 | 16.44% | Fit |
| 90 | 20.15% | Average |
| 100 | 26.75% | Above average |
| 110 | 32.5% | Above average |
How the estimate works
The US Navy formula relates body fat to the logarithms of the circumference measurements and height, all in centimetres. For men it is 495 ÷ (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450. For women it uses waist plus hip minus neck, with different constants.
A man 178 cm tall with a 38 cm neck and a 90 cm waist gets an estimate of 20.1%. A woman 165 cm tall with a 33 cm neck, a 75 cm waist and 98 cm hips gets 28.4%. Changing only the waist of the first man from 90 cm to 100 cm raises the estimate to 26.7%, and 80 cm lowers it to 12.4%.
Reading your category
The categories on this page are general ranges, not diagnoses. For men: below about 6% is essential fat or lower, 6–14% athletic, 14–18% fit, 18–25% average and above 25% above average. For women the boundaries are about 14%, 21%, 25% and 32%. Women naturally carry more essential fat than men.
Healthy ranges also depend on age. Body fat tends to rise with age, and ranges used by doctors and sports bodies differ. Use these categories for orientation and talk to a health professional about your goals.
Getting consistent measurements
The result depends on small differences in the tape measure. A one-centimetre error in the waist can move the estimate by about 0.7 of a percentage point. Measure in the morning before eating, keep the tape level and snug without compressing the skin, breathe out normally, and take each measurement two or three times and average them.
For tracking, consistency matters more than the absolute number. Use the same method, time of day and tape each time.
Limits of the method
The Navy method is an estimate. It can be off by several percentage points, especially for very muscular or very lean people, for older adults and for body shapes unlike those the formula was built on. Methods such as DEXA scans, underwater weighing or skinfold measurements by a trained person are more precise.
This is a general information tool, not medical advice. If you have health concerns about your weight or body composition, speak to a doctor.
Frequently asked questions
How accurate is the US Navy body fat method?
It is an estimate and can be off by several percentage points. Scans such as DEXA are more accurate.
Where do I measure my waist?
Men measure at the navel. Women measure at the narrowest point of the waist. Keep the tape level.
What is a healthy body fat percentage?
It depends on age and sex. The categories shown are general ranges, not medical advice.
Why do women need a hip measurement?
The formula for women includes the hips, because fat is distributed differently and this improves the estimate.
Is body fat better than BMI?
It gives different information. BMI uses only height and weight, while body fat estimates composition. Neither is a complete picture of health.
How often should I measure?
Every few weeks is enough. Daily changes are mostly measurement noise.
This calculator gives estimates for information only. Actual figures from a bank, employer, tax authority or doctor may differ. It is not financial, tax, legal or medical advice.