Quick answer: A man 178 cm tall with a 38 cm neck and 86 cm waist has about 17.2% body fat by the US Navy formula, which is in the ACE "fitness" range for men (14–17%).
How it's calculated
Men: body fat % = 495 ÷ (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450, with all measurements in cm. Women add the hips: 495 ÷ (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450.
In inches the US Department of Defense uses the equivalent form: men 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76; women 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387. The two forms give results within a few tenths of a percent.
Fat mass is your weight times the body fat percentage; the rest is lean mass (muscle, bone, organs and water). See the lean body mass calculator for estimates from height and weight alone.
The method was fitted against underwater weighing and is accurate to roughly ±3–4 percentage points for most people. It cannot tell where fat is stored (visceral fat around organs matters more for health than fat under the skin), and it is less reliable for very lean, very muscular or very large bodies.
Worked examples
- Man, 178 cm, neck 38 cm, waist 86 cm: 495 ÷ (1.0324 − 0.19077·log10(48) + 0.15456·log10(178)) − 450 = 17.2%
- Woman, 165 cm, neck 33 cm, waist 72 cm, hips 98 cm: 495 ÷ (1.29579 − 0.35004·log10(137) + 0.221·log10(165)) − 450 = 26.9%
- Man, 70 in, neck 15 in, waist 34 in: 86.010·log10(19) − 70.041·log10(70) + 36.76 = 17.5%
Body fat categories (American Council on Exercise)
| 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 above | 25% and above |
How to measure
- Height: barefoot, standing straight.
- Neck: just below the larynx (Adam's apple), tape sloping slightly down to the front.
- Waist: men at the level of the navel; women at the narrowest point of the abdomen. Measure after a normal breath out.
- Hips (women): at the widest point of the buttocks, feet together.
Frequently asked questions
How accurate is the US Navy method?
For most adults it is within about 3 to 4 percentage points of laboratory methods such as underwater weighing or DEXA. Measuring the same way each time matters more than the exact number.
Why do women need a hip measurement?
Women store more fat around the hips and thighs, so the women's equation adds the hip circumference to predict body fat better.
Is this the same as the Army tape test?
No. Since 2023 the US Army uses a one-site waist and weight formula. Use the US Army body fat calculator for that standard.
What is a healthy body fat percentage?
There is no single official cut-off. The ACE ranges above are widely used: about 14–24% for men and 21–31% for women covers the fitness and average groups.
How do I take the measurements?
Use a soft tape on bare skin without pressing in. Measure the neck just below the larynx and the waist at the level given on the form; women also measure the hips at their widest point. Take each one twice.
How is body fat different from BMI?
BMI uses only height and weight, so it can't tell fat from muscle. This method uses body measurements, so it usually gives a fairer picture for muscular people.