Body Fat % (US Navy)
Body fat from circumferences (%). Male uses waist & neck; female also hip.
How it works
Male: % = 495 ÷ (1.0324 − 0.19077×log₁₀(waist−neck) + 0.15456×log₁₀(height)) − 450 Female: % = 495 ÷ (1.29579 − 0.35004×log₁₀(waist+hip−neck) + 0.221×log₁₀(height)) − 450 (cm)
The US Navy method estimates body fat from neck, waist (and hip for women) circumferences — closer to actual fat than BMI alone, but still approximate.
Healthy body fat is roughly 10%–20% for men and 18%–28% for women (varies with age).
FAQ
What body fat is normal?
Roughly 10%–20% for men and 18%–28% for women, rising with age; athletes are usually lower.
Worked example
Male, height 175 cm, waist 85 cm, neck 38 cm (US Navy method, in cm):
BF% = 495 ÷ (1.0324 − 0.19077×log₁₀(85−38) + 0.15456×log₁₀175) − 450 ≈ 17%
That is roughly 11.9 kg of fat and 58.1 kg lean mass at 70 kg body weight.
Notes and limitations
Tape-based methods typically carry ±3–5 percentage points of error and are sensitive to tape placement, timing of exhalation and tightness. Measure in the morning, fasted, at the same spot. Error grows at very high or very low body fat; use DEXA when precision matters. Day to day, follow the trend, not the absolute number.