Breakdown
How it works
Developed for the US Navy, the formula uses the log of circumference differences. Men: waist and neck; women: waist, hip and neck. It tracks change well over time if you measure consistently (same time of day, relaxed, after exhaling).
Formula
Men: 495 ÷ (1.0324 − 0.19077 log(waist − neck) + 0.15456 log(height)) − 450
Women: 495 ÷ (1.29579 − 0.35004 log(waist + hip − neck) + 0.22100 log(height)) − 450
Worked example
Male 175 cm, neck 38, waist 88: 19.2% — "fit"; fat mass 15.4 kg, lean 64.6 kg.
Frequently asked questions
What is a healthy body fat?
Men 10–20%, women 18–28% for general health; athletes lower. Essential fat is ~3% men, ~12% women.
How does this compare with scales or DEXA?
Bio-impedance scales vary ±5% with hydration; DEXA is the gold standard. The Navy method is closer to DEXA than most scales.
Why does waist-to-height matter?
Keeping waist under half your height is a strong predictor of metabolic risk independent of weight.