📏 Body Fat Calculator
Estimate your body fat percentage using the US Navy method. All you need is a tape measure — no calipers or expensive equipment required.
How the Body Fat Calculator Works
This calculator uses the US Navy circumference method, developed by Hodgdon and Beckett at the Naval Health Research Center. It estimates body fat percentage from tape measurements using logarithmic formulas.
US Navy Body Fat Formulas
| Gender | Formula |
|---|---|
| Male | BF% = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76 |
| Female | BF% = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387 |
All measurements in cm. Imperial values are converted to cm automatically.
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% |
| Above Average | 25%+ | 32%+ |
How to Measure
- Waist — Measure horizontally at the navel (men) or narrowest point (women)
- Neck — Measure at the narrowest point, just below the larynx
- Hip (women only) — Measure at the widest point of the buttocks
- Use a flexible tape measure, snug but not compressing the skin
- Measure in the morning, before eating, for consistency
Frequently Asked Questions
The US Navy method is accurate within 1-3% of DEXA scan results for most people. It's the most practical and reliable tape-measure based method available, used by military organizations worldwide.
For men, measure horizontally at the navel (belly button) level. For women, measure at the narrowest point of the waist, typically just above the navel. Keep the tape snug but not compressing the skin.
For men: 10-20% is considered fit, 14-17% is the ideal fitness range. For women: 18-28% is fit, 21-24% is ideal. Essential fat minimums are 3-5% for men and 10-13% for women.
Women naturally carry more essential fat for reproductive functions, hormonal balance, and breast tissue. Essential fat for women is 10-13% compared to 3-5% for men. This is completely normal and healthy.
Measure every 2-4 weeks at the same time of day (morning, before eating). Body fat changes slowly, so more frequent measurements will just show normal daily fluctuations.
Body fat percentage is generally more useful because it distinguishes between muscle and fat mass. A muscular person can have a "overweight" BMI but a perfectly healthy body fat percentage.