About the body fat calculation
Body fat percentage tells you what BMI cannot: how much of your weight is actually fat. The US Navy method uses tape measurements and is accurate to roughly ±3% against DEXA scanning — good enough to track direction over time, which is what matters.
Formula
Men:
%BF = 495 ÷ (1.0324 − 0.19077×log₁₀(waist − neck) + 0.15456×log₁₀(height)) − 450
Women:
%BF = 495 ÷ (1.29579 − 0.35004×log₁₀(waist + hip − neck) + 0.22100×log₁₀(height)) − 450
All measurements in centimetres.Worked example
A man 175 cm tall with a 38 cm neck and 85 cm waist: log₁₀(47) = 1.6721 and log₁₀(175) = 2.2430, giving roughly 18% body fat.
Frequently asked questions
How accurate is the Navy method?
Within about 3 percentage points of a DEXA scan for most people. It is least accurate at the extremes — very lean or very obese — and it assumes typical fat distribution, so unusual body shapes will read further off.
How should I take the measurements?
Use a flexible tape, keep it level and snug without compressing the skin, and measure at the same time of day. Neck goes just below the larynx; waist at the navel for men and at the narrowest point for women; hips at the widest point.
What is a healthy body fat percentage?
For men, roughly 14-18% is a fitness range and 18-25% is average. For women it is 21-25% and 25-32% respectively, because women carry more essential fat. Below about 6% for men and 14% for women is essential fat and is not safe to sustain.
Sources
- Hodgdon JA, Beckett MB — US Navy circumference method (1984)
- Deurenberg P, et al. — Body mass index as a measure of body fatness (1991)