Body Fat Calculator
Body-fat percentage from tape measurements, by the US Navy method.
How to use Body Fat Calculator
- Choose units and enter sex, age, weight and height.
- Measure your neck just below the larynx, and your waist: at the navel for men, at the narrowest point for women. Women also measure the hips at the widest point.
- Enter the measurements in the same units and read your estimated body fat.
How it works
The US Navy circumference method (Hodgdon and Beckett, Naval Health Research Center, 1984) estimates body density from tape measurements. In centimetres: men 495 ÷ (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450; women 495 ÷ (1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.22100 × log₁₀(height)) − 450. Inches are converted to centimetres first.
Fat mass is your weight × the percentage, and lean mass is the rest. The category uses the American Council on Exercise ranges shown in the table. For comparison the tool also shows the Deurenberg estimate from BMI and age (1.20 × BMI + 0.23 × age − 10.8 × sex − 5.4, sex = 1 for men), which is rougher.
Example
A man 178 cm tall with a 38 cm neck and 86 cm waist: 495 ÷ (1.0324 − 0.19077 × log₁₀(48) + 0.15456 × log₁₀(178)) − 450 ≈ 17.2%, in the "Fitness" range.
Frequently asked questions
How accurate is the Navy method?
For most people it is within about 3–4 percentage points of laboratory methods such as DEXA. It can be less accurate for very lean, very muscular or older people. Measure carefully and use it to track change over time.
Where exactly do I measure?
Neck: just below the larynx, tape sloping slightly down at the front. Waist: men at the navel, women at the narrowest point. Hips (women): the widest point. Keep the tape level and snug without pressing into the skin, and measure on bare skin.
What is a healthy body-fat percentage?
By the ACE ranges, 14–24% for men and 21–31% for women cover "fitness" and "average". Essential fat is about 2–5% for men and 10–13% for women; going below it is unhealthy.
Is this better than BMI?
It answers a different question. BMI compares weight with height and cannot tell muscle from fat. A tape-measure estimate adds information about body shape, which is why both are shown.
Limitations
- An estimate from body shape, not a measurement of fat.
- Not for children or pregnancy.
- An estimate for healthy adults, not medical advice. Talk to a doctor or registered dietitian about your own situation.
Last reviewed November 9, 2026. How we build and test tools.