How the body fat calculator works
The US Navy method predicts body density from a few circumference measurements and your height, then converts density to a body fat percentage. Measurements are in centimetres; the calculator converts inches for you.
Men: 495 ÷ (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450
Women: 495 ÷ (1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.221 × log₁₀(height)) − 450
Worked example
A man who is 178 cm (5 ft 10 in) tall with a 38 cm neck and an 86 cm waist:
- Waist minus neck: 86 − 38 = 48 cm. log₁₀(48) = 1.681.
- log₁₀(178) = 2.250.
- Density part: 1.0324 − 0.19077 × 1.681 + 0.15456 × 2.250 = 1.0595.
- Body fat: 495 ÷ 1.0595 − 450 = about 17.2%, in the fitness range for men.
Body fat categories
The American Council on Exercise groups body fat percentages like this:
| Category | Women | Men |
|---|---|---|
| Essential fat | 10–13% | 2–5% |
| Athletes | 14–20% | 6–13% |
| Fitness | 21–24% | 14–17% |
| Average | 25–31% | 18–24% |
| Obese | 32% and over | 25% and over |
Frequently asked questions
How accurate is the US Navy body fat method?
Studies generally find tape-measure methods like this one within a few percentage points of lab methods such as underwater weighing or DEXA scans for most people. Careful, consistent measuring matters more than anything else.
What is a healthy body fat percentage?
On the American Council on Exercise chart, an average range is 18–24% for men and 25–31% for women, and the fitness range is 14–17% for men and 21–24% for women. Some fat is essential: about 2–5% for men and 10–13% for women.
Why do women need a hip measurement?
Women tend to carry more fat around the hips and thighs, so the women’s equation adds the hip measurement to the waist to predict body fat more accurately.
How should I measure?
Use a flexible tape on bare skin, snug but not compressing the skin, and keep it level. Measure the neck just below the larynx, the waist at the navel for men or the narrowest point for women, and the hips at their widest. Take each measurement twice and use the average.
What is the difference between body fat and BMI?
BMI only compares weight with height. Body fat percentage estimates how much of your weight is fat, so it can tell apart two people with the same BMI but different builds.
Sources
Body fat estimates from tape measurements can be off by several percentage points. This calculator is for general information and is not medical advice. Read the full disclaimer and how we check our formulas.