Body Fat Calculator
Estimate your body fat percentage from simple tape measurements using the US Navy method.
Last reviewed July 1, 2026
A circumference-based estimate — handy for tracking change over time, but less precise than a DEXA scan. Not medical advice.
Body fat percentage tells you more about your health and fitness than weight alone. This calculator uses the US Navy circumference method — just a tape measure and a few body measurements — to estimate your body fat percentage and category.
Enter your height and the circumference of your neck and waist (plus hips for women). It's a quick, no-equipment way to track changes over time.
The Body Fat formula
Men: BF% = 495 ÷ (1.0324 − 0.19077·log₁₀(waist − neck) + 0.15456·log₁₀(height)) − 450; Women: BF% = 495 ÷ (1.29579 − 0.35004·log₁₀(waist + hip − neck) + 0.22100·log₁₀(height)) − 450waist, neck, hip and height are circumference and height measurements in centimetres (the US Navy method uses log base 10). Women include the hip measurement; men do not.
Worked example
For a man 180 cm tall with an 85 cm waist and 38 cm neck: log₁₀(85 − 38) = log₁₀(47) ≈ 1.672 and log₁₀(180) ≈ 2.255. BF% = 495 ÷ (1.0324 − 0.19077×1.672 + 0.15456×2.255) − 450 ≈ 16%.
How to take the measurements
Measure with a soft tape, snug but not compressing the skin. Neck: just below the larynx. Waist: at the navel for men, at the narrowest point for women. Hips (women): at the widest point.
Measure in the morning before eating for the most consistent readings, and take each measurement twice, using the average.
How accurate is it?
The US Navy method is convenient and reasonably good for tracking trends, but it's an estimate — less precise than a DEXA scan or hydrostatic weighing. Its real strength is consistency: measure the same way each time and the change over weeks is meaningful, even if the absolute number is a few points off.
Frequently asked questions
▶What is a healthy body fat percentage?
It varies by sex and age. Broadly, fitness ranges are around 14–18% for men and 21–25% for women, with athletes lower. The calculator shows your category alongside the number.
▶Why does the female formula need a hip measurement?
Women typically carry more fat around the hips, so the US Navy formula includes hip circumference to improve accuracy for women.
▶How does the US Navy body fat formula work?
It estimates body fat from the log of your circumference measurements — waist and neck for men, plus hips for women — relative to your height. No calipers or scales are needed, just a tape measure.
▶Is body fat percentage a better measure than BMI?
For assessing fitness it often is, because it distinguishes fat from muscle, which BMI can't. But circumference estimates are still approximate — use them to track trends over time.
▶How often should I measure my body fat?
Every two to four weeks is plenty. Measure the same way each time, ideally in the morning before eating, so changes reflect real progress rather than day-to-day fluctuation.
▶What's the most accurate way to measure body fat?
Lab methods like DEXA scans and hydrostatic weighing are the most accurate. The US Navy tape method trades some precision for being free, quick and repeatable at home.
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Open calculator →Disclaimer: Body Fat Calculator results are estimates for general information and education only, and are not financial, tax, legal or medical advice. Verify important decisions with a qualified professional.