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Body Fat Calculator (US Navy Method)
Estimate your body fat percentage from neck, waist and hip measurements. Good for tracking change over time with only a tape measure.
The formula
The US Navy method estimates body fat from circumferences and height (inches):
Men: %BF = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76Women: %BF = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387
The calculator converts centimetres to inches for you.
How to measure correctly
- Measure in the morning, before eating, in the same spot each time.
- Neck: just below the larynx, tape sloping slightly down toward the front. Do not flare your neck.
- Waist: men at the navel; women at the narrowest point, usually above the navel. Relax and breathe out normally.
- Hip (women): at the widest point of the buttocks.
- Keep the tape snug without pressing into the skin. Take each measurement three times and average them.
Pro tip: a 1 cm waist error can shift the result by about 1 percentage point, so consistency matters more than perfection.
Body fat ranges (American Council on Exercise)
| Category | Men | Women |
|---|---|---|
| Essential fat | 2 to 5% | 10 to 13% |
| Athletes | 6 to 13% | 14 to 20% |
| Fitness | 14 to 17% | 21 to 24% |
| Average | 18 to 24% | 25 to 31% |
| Obese | 25% and above | 32% and above |
These ranges were developed mostly in Western populations. Some Asian populations carry higher health risk at lower body fat, so discuss your result with a clinician rather than relying on the label alone.
How accurate is it?
The Navy method is a prediction from tape measurements. Expect an error of several percentage points compared with a DEXA scan, and it can mislead very muscular or very lean people. Its strength is repeatability: use the same method every 2 to 4 weeks and watch the direction of change.
Next steps
- Pair the result with your BMI and waist-to-height ratio.
- Enter your body fat in the BMR calculator to see the Katch-McArdle estimate.
- If you need an exact figure for medical or athletic reasons, ask about a DEXA scan.
Medical disclaimer: This tool is for education and general planning. It is not medical advice and does not diagnose any condition. If you are pregnant, under 18, have an eating-disorder history or a medical condition, speak to a doctor or registered dietitian before changing your diet or exercise.
Frequently asked questions
What is a healthy body fat percentage?
For many adults roughly 14% to 24% for men and 21% to 31% for women falls in the fitness-to-average range, but healthy levels vary with age, ethnicity and health status.
Is the Navy method accurate?
It is reasonable for tracking trends but can be off by several percentage points compared with DEXA.
Why do women need a hip measurement?
The formula for women adds hip circumference, which reflects the different pattern of fat distribution.
How often should I measure?
Every 2 to 4 weeks. Daily changes are mostly noise.
Can I use this if I am pregnant?
No. The formula is not valid during pregnancy.
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References and sources
- Hodgdon JA, Beckett MB (1984). Prediction of percent body fat for U.S. Navy men and women from body circumferences and height. Naval Health Research Center reports.
- American Council on Exercise. Percent body fat norms for men and women (category ranges). Link