The U.S. Navy body fat formula
The U.S. Navy method estimates body fat from height and a few circumferences. Hodgdon and Beckett developed it at the Naval Health Research Center in 1984, and the U.S. military still uses it because it needs nothing more than a tape measure.
The formula for men
%BF = 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76
Measurements in inches. The waist is measured horizontally at the navel.
The formula for women
%BF = 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387
Measurements in inches. The waist is measured at its narrowest point and the hips at their widest.
Metric version
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
Measurements in centimeters. This version predicts body density and converts it to body fat with the Siri equation. It gives practically the same result as the inch version.
Worked example
A man 178 cm tall with a 39 cm neck and an 88 cm waist: waist − neck = 49 cm. Body density = 1.0324 − 0.19077 × log₁₀(49) + 0.15456 × log₁₀(178) = 1.0578. Body fat = 495 ÷ 1.0578 − 450 ≈ 18.0%.
How accurate is it?
Compared with underwater weighing, the Navy equations have a standard error of about 3 to 4 percentage points. They work best for people of typical build: a very muscular neck or unusual fat distribution can shift the result.
Measure consistently, with the same tape, at the same spot and the same time of day, and focus on the trend over time.
Sources
- Hodgdon JA, Beckett MB (1984). Prediction of percent body fat for U.S. Navy men and women from body circumferences and height. Naval Health Research Center, Reports 84-11 and 84-29.
- Siri WE (1961). Body composition from fluid spaces and density: analysis of methods. In: Techniques for Measuring Body Composition. Washington, DC: National Academy of Sciences.