The US Navy body-fat formula
The US Navy method estimates body fat from a few tape measurements and height, all in inches, using a logarithmic regression. For men:
BF% = 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76
For women, hip circumference is added in:
BF% = 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387
Worked example
A man 70 in tall with a 16 in neck and 34 in waist:
Waist − neck: 34 − 16 = 18.
86.010 × log₁₀(18): 86.010 × 1.2553 ≈ 107.97.
70.041 × log₁₀(70): 70.041 × 1.8451 ≈ 129.24.
Body fat: 107.97 − 129.24 + 36.76 ≈ 15.5%.
Typical body-fat ranges (ACE)
| 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%+ |
Tip: measure at the navel for waist, below the larynx for neck, and at the widest point for hips. Keep the tape snug but not compressing the skin, and measure on bare skin for consistency.