Body fat calculator
BMI cannot tell fat from muscle. This calculator estimates your body fat percentage with the U.S. Navy circumference method — all you need is a tape measure — and compares it with a BMI-based estimate.
How body fat is estimated
U.S. Navy method (Hodgdon & Beckett, 1984) uses height and neck and waist circumference (plus hips for women) in a logarithmic equation. Its typical error is a few percentage points compared with laboratory methods, so measure carefully and use the same technique each time.
BMI-based estimate (Deurenberg, 1991): 1.20 × BMI + 0.23 × age − 10.8 × sex − 5.4 (sex = 1 for men, 0 for women). It does not use body measurements, so it overestimates fat in muscular people.
Body fat categories (ACE)
| Weight Category | Female | Male |
|---|
| Essential fat | 10–13% | 2–5% |
| Athletes | 14–20% | 6–13% |
| Fitness | 21–24% | 14–17% |
| Average | 25–31% | 18–24% |
| Obesity | ≥ 32% | ≥ 25% |
Frequently asked questions
What is a healthy body fat percentage?
According to the American Council on Exercise, 25–31% is average for women and 18–24% for men; the fitness range is 21–24% for women and 14–17% for men.
Why do the two methods give different results?
The Navy method uses your measurements, while the BMI method only uses weight, height, age and sex. If you are muscular, trust the Navy result more.
How often should I measure?
Every 2–4 weeks is enough. Measure in the morning before eating, at the same places on your body and with the same tape.
