How to work out your body fat percentage
- Choose Metric or US units and your Sex.
- Measure and enter your height, Neck and Waist. Women also enter Hips; men can ignore that box.
- Add your weight if you want fat mass and lean mass, then read your body fat percentage and its category.
How to measure
Use a soft tape measure, stand relaxed and breathe out normally before you read the tape. Keep it level and snug against the skin without pressing in. Measure each spot two or three times and use the average.
| Measurement | Where to put the tape |
|---|---|
| Neck | Just below the Adam’s apple (the larynx), sloping slightly down towards the front |
| Waist, men | Level around the belly at the navel |
| Waist, women | At the narrowest point of the waist, usually a little above the navel |
| Hips, women | Around the widest part of the buttocks, feet together |
Height should be without shoes. Measure at the same time of day each time you check, because waist size changes after meals.
The formula and an example
The calculator uses the U.S. Navy equations with measurements in centimetres:
- Men: 495 ÷ (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450
- Women: 495 ÷ (1.29579 − 0.35004 × log10(waist + hips − neck) + 0.221 × log10(height)) − 450
A man who is 178 cm tall with a 38 cm neck and an 86 cm waist comes out at 17.2% body fat. At 80 kg that is 13.8 kg of fat and 66.2 kg of lean mass. A woman who is 165 cm with a 33 cm neck, 74 cm waist and 98 cm hips comes out at 27.9%.
| ACE category | Women | Men |
|---|---|---|
| Essential fat | below 14% | below 6% |
| Athletes | 14 to 20% | 6 to 13% |
| Fitness | 21 to 24% | 14 to 17% |
| Average | 25 to 31% | 18 to 24% |
| Obese | 32% and over | 25% and over |