Body Fat Calculator
Estimate your body fat percentage with the U.S. Navy circumference method.
How to use
- Choose your sex.
- Enter height, neck and waist (and hip for women) in centimetres.
- Your estimated body fat percentage updates instantly.
How the Body Fat Calculator works
Estimates body fat percentage from tape measurements using the US Navy circumference method — no calipers or scales required.
The Navy formula uses the logarithm of circumference measurements relative to height. Men use neck and waist; women add hip, because fat distribution differs enough that a single equation would not fit both.
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
Worked example
A man 180 cm tall with a 38 cm neck and 85 cm waist comes out near 15% body fat.
Things worth knowing
- Typical ranges for men: 6–13% athletic, 14–17% fit, 18–24% average, 25%+ obese. For women, add roughly 8–10 points to each band — essential fat is higher.
- Measurement technique dominates accuracy. Measure at the same point each time, tape snug but not compressing, and ideally first thing in the morning.
- The method is accurate to roughly ±3–4% against DEXA. It is far better at tracking change over time than at pinning down an exact figure.
Frequently asked questions
How accurate is the Navy method?
It's a solid estimate from tape measurements, though body scans like DEXA are more precise.
Where do I measure?
Neck below the larynx, waist at the navel, and hips at the widest point.
Why do women need a hip measurement?
Women carry proportionally more fat on the hips and thighs, so waist alone would systematically underestimate it.