U.S. Navy body fat formula
All measurements are in inches:
Men: %BF = 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76
Women: %BF = 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387
Women: %BF = 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387
Fat mass = weight × %BF ÷ 100, and lean mass = weight − fat mass.
Example: A man 5 ft 10 in (70 in) tall with a 15 in neck and 34 in waist: 86.010 × log₁₀(19) − 70.041 × log₁₀(70) + 36.76 = 17.5% body fat — in the “fitness” range. At 176 lb that is about 31 lb of fat and 145 lb of lean mass.
Body fat categories (ACE)
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletes | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Obese | 25% + | 32% + |
Tips for consistent results
- Measure in the morning, before eating, with a flexible non-stretch tape.
- Take each measurement three times and use the average.
- Track the trend every 2–4 weeks rather than day to day.
Compare with your BMI, which uses only height and weight.
Frequently asked questions
How accurate is the U.S. Navy body fat method?
Compared with lab methods such as DEXA, tape-measure formulas are typically accurate to within about 3–4 percentage points for most people. Accuracy depends heavily on measuring the same way each time.
Where exactly should I measure?
Neck: just below the larynx (Adam’s apple), tape sloping slightly down to the front. Waist: men at the navel; women at the narrowest point of the natural waist. Hips (women): at the widest point of the buttocks. Keep the tape snug but not compressing the skin, and measure relaxed, not sucking in.
What is a healthy body fat percentage?
According to the American Council on Exercise, “fitness” levels are 14–17% for men and 21–24% for women, and “average” is 18–24% for men and 25–31% for women. Essential fat — the minimum for normal body function — is about 2–5% for men and 10–13% for women.
Why do women need a hip measurement?
Women typically store more fat around the hips and thighs, so the Navy formula for women uses the sum of waist and hip circumference minus the neck.