Body Fat
Calculate body fat percentage using the US Navy method
These calculators provide general information only and are not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider.
How to use Body Fat
- 1Select your sex and unit system. Sex directly changes the formula coefficients.
- 2Enter height, weight and age. If you know your neck and waist circumference, add them for a noticeably better estimate.
- 3Read the estimated body fat percentage, see which band it falls into, and compare it with the table below.
How body fat percentage is estimated
Body fat (%) = fat mass ÷ body weight × 100Body fat percentage is the share of your total weight that is fat, and it describes body composition more directly than BMI. This tool uses the US Navy method, which derives body fat from height, neck and waist circumference. When circumference data is missing it falls back to the Deurenberg equation: body fat = 1.20 × BMI + 0.23 × age − 10.8 × sex − 5.4, where sex is 1 for male and 0 for female.
Results from different methods can differ by 3 to 5 percentage points. Home scales use bioelectrical impedance, which reacts strongly to hydration, food and exercise. Underwater weighing and DXA scans are more accurate but impractical for daily use. Treat body fat percentage as a long-term trend: measure under consistent conditions, ideally in the morning before eating, and compare changes over several weeks rather than a single reading.
| Group | Essential | Athlete | Fitness | Average | Obese |
|---|---|---|---|---|---|
| Male | 2–5% | 6–13% | 14–17% | 18–24% | ≥ 25% |
| Female | 10–13% | 14–20% | 21–24% | 25–31% | ≥ 32% |
Body fat reference ranges (ACE)
Frequently asked questions
Which is more accurate, a body fat scale or this calculator?
Both are estimates with different error sources. Impedance scales react strongly to hydration, so readings swing after drinking or exercising. The circumference method here depends on how carefully you measure. Pick one method, keep conditions consistent, and watch the long-term trend.
Why does my body fat reading disagree with my BMI?
That is exactly the point of measuring body fat. BMI only relates weight to height and cannot tell muscle from fat, while body fat estimates the fat share directly. Muscular people are often labelled overweight by BMI despite healthy body fat, and in that case body fat is the better guide.
Is lower body fat always better?
No. Fat supports hormone production, temperature regulation and absorption of fat-soluble vitamins. Staying below roughly 5% for men and 13% for women over long periods can disrupt hormones and immunity. The fitness or average bands are usually the sustainable target.
When is the best time to measure?
Measure in the morning, fasted and after using the bathroom, and avoid measuring right after hard training: dehydration pushes impedance readings up and temporary swelling inflates circumference. Averaging three consecutive days is far more reliable than one reading.