About the body fat calculator
This calculator uses the circumference method developed by the U.S. Navy. It needs only a tape measure: neck and waist for men, and neck, waist and hip for women, together with your height. The measurements are converted to a body density estimate and then to a body fat percentage.
The result is shown with your fat mass, lean mass and a category from the American Council on Exercise (essential fat, athletes, fitness, average, obese). For comparison it also shows an estimate based on BMI and age. The two methods often disagree by a few points, which is normal.
Tape-measure methods are accurate to roughly 3 to 4 percentage points. For the most repeatable result, measure at the same time of day, keep the tape snug without compressing the skin, and take each measurement twice.
Formula
- Men: % fat = 495 ÷ (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450
- Women: % fat = 495 ÷ (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450
- All lengths in centimetres
- Fat mass = weight × % fat ÷ 100
Example
A man who is 177.8 cm tall with a 38.1 cm neck and an 86.4 cm waist has a Navy body fat of about 17.5%. At 72.57 kg that is roughly 12.7 kg of fat and 59.9 kg of lean mass.