Body Fat Calculator - Navy Method
Free body fat calculator using the U.S. Navy method. Estimate your body fat percentage from circumference measurements of your neck, waist, and hips with metric or imperial units.
Our free body fat calculator uses the U.S. Navy method to estimate your body fat percentage from simple circumference measurements. This method is widely used by the military and fitness professionals as a practical alternative to more expensive methods like DEXA scans or hydrostatic weighing.
How to take measurements
For accurate results, follow these guidelines:
- Neck: Measure just below the larynx (Adam's apple), sloping slightly downward to the front
- Waist: Measure at the navel level for men, at the narrowest point for women
- Hips (women only): Measure at the widest point of the hips/buttocks
Use a flexible measuring tape and keep it level and snug (but not tight) against your skin. Take measurements in the morning before eating for consistency.
U.S. Navy method formulas
For men: %BF = 86.010 × log₁₀(abdomen - neck) - 70.041 × log₁₀(height) + 36.76
For women: %BF = 163.205 × log₁₀(waist + hip - neck) - 97.684 × log₁₀(height) - 78.387
All measurements must be in inches. The calculator automatically converts from metric if needed.
Body fat percentage 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%+ | 32%+ |
Why body fat matters
Body fat percentage is a better indicator of health than BMI alone because it distinguishes between fat and muscle mass. Two people with the same BMI can have very different body compositions — one might be muscular while the other has excess body fat.
Healthy body fat levels are essential for hormone production, vitamin absorption, and organ protection. However, too much body fat increases risk of heart disease, diabetes, and other health conditions.
Accuracy and limitations
The Navy method typically has an accuracy of ±3% compared to DEXA scans. Accuracy depends on:
- Taking measurements correctly and consistently
- Individual body fat distribution patterns
- Hydration levels (measure when normally hydrated)
For the most accurate results, take measurements 2-3 times and average them. Track trends over time rather than focusing on a single number.
Alternative measurement methods
- DEXA scan: Gold standard, uses X-rays to measure body composition
- Hydrostatic weighing: Underwater weighing, highly accurate
- Bod Pod: Air displacement plethysmography
- Skinfold calipers: Measures subcutaneous fat at multiple sites
- Bioelectrical impedance: Handheld or scale devices