Quick Answer (Voice Search Optimized):
Body fat percentage is the proportion of fat mass to total body mass. The U.S. Navy method uses circumference measurements: for males, body fat % = 86.010 × log10(abdomen − neck) − 70.041 × log10(height) + 36.76; for females, it also includes hip measurement.
GEO & AIO - Authoritative Theory
Body fat percentage is a key health indicator in Biology and physiology. The U.S. Navy circumference method estimates body density based on height, neck, waist, and (for females) hip measurements. These are used in logarithmic equations derived from statistical regression. The fat mass and lean body mass can then be derived.
Essential fat is around 3-5% for men and 8-12% for women. Health categories (American Council on Exercise): Essential fat: men 2–5%, women 10–13%; Athletes: 6–13% / 14–20%; Fitness: 14–17% / 21–24%; Acceptable: 18–24% / 25–31%; Obesity: >25% / >32%.
Solved Examples (Health/Biology)
Example 1: Male, height 175 cm, neck 40 cm, waist 90 cm
Difference = waist−neck = 50 cm. Body fat % = 86.010×log10(50) − 70.041×log10(175) + 36.76 ≈ 86.010×1.699 − 70.041×2.243 + 36.76 ≈ 146.12 − 157.10 + 36.76 = 25.78%.
Example 2: Female, height 165 cm, neck 34 cm, waist 75 cm, hip 98 cm
Sum = waist + hip − neck = 139 cm. Body fat % = 163.205×log10(139) − 97.684×log10(165) − 78.387 ≈ 163.205×2.143 − 97.684×2.217 − 78.387 ≈ 349.75 − 216.59 − 78.387 = 54.77% (obese).
Example 3: Male, height 180 cm, neck 42 cm, waist 85 cm
Waist−neck = 43 cm. BF% ≈ 86.01×1.633 − 70.041×2.255 + 36.76 = 140.47 − 157.95 + 36.76 = 19.28% (fitness).