EXAMPLE
A 180cm male with a 38cm neck and 85cm waist comes to about 16.1% body fat.
Enter your measurements to see results.
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How this calculator works
Body fat percentage estimates how much of body weight is fat versus lean mass, which BMI cannot distinguish on its own. This calculator uses the US Navy circumference method — height, neck, and waist (plus hip for women) — to estimate body fat without special equipment.
THE MATH BEHIND IT
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
A real example
A male, 180 cm tall, with a 38 cm neck and 85 cm waist:
waist − neck
85 − 38 =47 cm
Estimated body fat
≈ 16.1%
Common questions
The US Navy method estimates body fat from circumference measurements rather than a skinfold caliper pinch. It was developed to be quick and repeatable without specialized equipment, using measurements that correlate with body fat percentage across large population studies.
Fat distribution patterns differ by sex, and the formula for women includes a hip measurement in addition to waist and neck to account for this. The two formulas were derived from separate population data sets.
Circumference-based methods like this one are generally considered accurate to within about 3–4 percentage points compared to more precise methods such as DEXA scans or hydrostatic weighing, which use direct measurement rather than a population-based formula.