Body Fat Calculator (US Navy Method)
Body fat % from tape measurements, with ACE category.
Measure the neck just below the larynx, the waist at the navel for men or at the narrowest point for women, and the hips at their widest point. Keep the tape level and snug without compressing the skin.
The tape-measure method is an estimate, typically within a few percentage points of lab methods such as DEXA, and less reliable at very low or high body fat. It is not a diagnosis; talk to a health professional about what your result means for you.
Use via API
Body fat percentage by the US Navy circumference method, with the ACE category and (given a weight) fat and lean mass. Send JSON, get JSON back.
POST https://pithlab.com/api/v1/tools/body-fat-calculator
curl https://pithlab.com/api/v1/tools/body-fat-calculator \
-H "Authorization: Bearer $PITHLAB_KEY" \
-H "Content-Type: application/json" \
-d '{"sex":"male","units":"metric","height":180,"neck":38,"waist":85,"weight":80}'About the Body Fat Calculator
Estimate body fat percentage from height, neck, waist and hip measurements with the US Navy tape method, plus your ACE category, fat mass and lean mass.
How to use the Body Fat Calculator
- Choose your units and sex.
- Measure and enter your height, neck and waist, plus hips for women. Add your weight if you want fat and lean mass.
- Read your estimated body fat percentage, where it sits in the ACE categories, and the split between fat and lean mass.
Examples
Input
male, 180 / 38 / 85 cm, 80 kg
Output
Body fat 16.2%: Fitness (ACE 14–17%); fat mass 12.9 kg, lean mass 67.1 kg
Input
female, 65 / 13 / 30 / 38 in, 140 lb
Output
Body fat 28.6%: Average (ACE 25–31%); fat mass 40.0 lb, lean mass 100.0 lb
Frequently asked questions
How does the US Navy method work?
It estimates body fat from circumferences using equations published by Hodgdon and Beckett in 1984. For men: 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76. For women: 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387, all in inches. Centimetres are converted to inches first.
How accurate is it?
For most adults it lands within about 3 to 4 percentage points of lab methods like DEXA, but it can be further out for very lean or very muscular people and for people carrying more weight. Measuring the same way each time matters more than the absolute number when tracking change.
Where exactly should I measure?
Neck just below the Adam's apple, with the tape sloping slightly down at the front. Waist at the navel for men and at the narrowest point for women. Hips at the widest point of the buttocks. Stand relaxed, don't suck in, and read the tape without compressing the skin.
What do the categories mean?
They are the American Council on Exercise ranges. Essential fat is the minimum needed for normal body function; athletes, fitness and average describe typical ranges; obese is 25% and above for men and 32% and above for women. They are a guide, not a diagnosis.