Body Fat Percentage Formula (Navy Method)
Estimate body fat percentage using the U.S.
Navy method with circumference measurements.
Separate formulas for men and women in metric and imperial.
The Formula
Men (using inches)
Women (using inches)
The U.S. Navy method estimates body fat percentage using simple circumference measurements.
It requires only a measuring tape — no special equipment needed.
Variables
| Symbol | Meaning |
|---|---|
| BF% | Body fat percentage |
| abdomen / waist | Waist circumference at the navel (inches or cm) |
| neck | Neck circumference below the larynx (inches or cm) |
| hip | Hip circumference at the widest point — women only (inches or cm) |
| height | Total height (inches or cm) |
| log₁₀ | Base-10 logarithm |
Unit Conversions
The formula above uses inches. To convert from centimetres:
- inches = cm ÷ 2.54
Alternatively, use the metric version of the formula (with cm) by substituting these coefficients:
- Men (cm): BF% = 86.010 × log₁₀(abdomen_cm - neck_cm) - 70.041 × log₁₀(height_cm) + 36.76
- Women (cm): BF% = 163.205 × log₁₀(waist_cm + hip_cm - neck_cm) - 97.684 × log₁₀(height_cm) - 78.387
Note: when using centimetres, the same coefficients apply because the logarithm accounts for the scale.
Body Fat Categories (Men)
| Category | Body Fat % |
|---|---|
| Essential fat | 2-5% |
| Athletic | 6-13% |
| Fit | 14-17% |
| Average | 18-24% |
| Above average | 25%+ |
Body Fat Categories (Women)
| Category | Body Fat % |
|---|---|
| Essential fat | 10-13% |
| Athletic | 14-20% |
| Fit | 21-24% |
| Average | 25-31% |
| Above average | 32%+ |
Example 1 (Men)
A man has a waist of 36 inches (91.4 cm), neck of 15.5 inches (39.4 cm), and height of 70 inches (177.8 cm).
BF% = 86.010 × log₁₀(36 - 15.5) - 70.041 × log₁₀(70) + 36.76
BF% = 86.010 × log₁₀(20.5) - 70.041 × log₁₀(70) + 36.76
BF% = 86.010 × 1.3118 - 70.041 × 1.8451 + 36.76
BF% = 112.83 - 129.23 + 36.76
BF% ≈ 20.4% — Average range
Example 2 (Women)
A woman has a waist of 30 inches (76.2 cm), hip of 38 inches (96.5 cm), neck of 13 inches (33 cm), and height of 65 inches (165.1 cm).
BF% = 163.205 × log₁₀(30 + 38 - 13) - 97.684 × log₁₀(65) - 78.387
BF% = 163.205 × log₁₀(55) - 97.684 × log₁₀(65) - 78.387
BF% = 163.205 × 1.7404 - 97.684 × 1.8129 - 78.387
BF% = 283.99 - 177.09 - 78.387
BF% ≈ 28.5% — Average range
When to Use It
Use the Navy body fat formula when you need to:
- Estimate body fat without expensive equipment
- Track body composition changes over time
- Get a more meaningful measurement than BMI alone
- Set realistic fitness and body composition goals
For the most accurate results, measure at the same time of day and in the same conditions each time.
This method has an accuracy of approximately ±3-4% compared to underwater weighing.
This formula is for general educational purposes only. It is not medical advice. Consult a healthcare professional for accurate body composition analysis.