How the U.S. Navy method works
The Navy formula estimates body fat from body circumferences and height, because fat around the waist relative to the neck tracks total body fat quite well. With a careful measurement it is typically within about 3–4 percentage points of laboratory methods.
♀ BF% = 495 ÷ (1.29579 − 0.35004·log₁₀(W + Hip − N) + 0.22100·log₁₀(H)) − 450
W = waist, N = neck, Hip = hips, H = height, all in centimetres. Example: a man 178 cm tall with a 38 cm neck and an 88 cm waist has about 18.7% body fat.
Body fat categories
| Result | Female | Male |
|---|---|---|
| Essential fat | 10–13% | 2–5% |
| Athletes | 14–20% | 6–13% |
| Fitness | 21–24% | 14–17% |
| Average | 25–31% | 18–24% |
| Obese | 32%+ | 25%+ |
Categories from the American Council on Exercise. Healthy body fat naturally rises a little with age, and women carry more essential fat than men.
Tips for accurate measurements
- Measure in the morning, before eating, on bare skin.
- Keep the tape level and snug without compressing the skin.
- Take each measurement two or three times and use the average.
Frequently asked questions
What is a healthy body fat percentage?
Roughly 14–24% for men and 21–31% for women is considered fit to average. Athletes are often lower; above 25% for men or 32% for women is classed as obese.
How accurate is the Navy body fat calculator?
For most people it is within about 3–4 percentage points of more precise methods such as DEXA, provided the measurements are taken carefully.
Why is my body fat different from the BMI estimate?
BMI doesn't distinguish fat from muscle. The tape method uses your waist and neck, so muscular people usually get a lower, more realistic figure.
This is an estimate for general information and not a medical assessment.