Body Fat Calculator estimates your body composition using the US Navy circumference method - a reliable way to track progress without expensive scans or calipers. This free online fat percentage tool requires only a standard tape measure to compute your fat mass and lean body mass, providing a more detailed health indicator than weight alone. While no formula is perfect, this body composition calculator offers ±3–4% accuracy compared to clinical standards.
The Navy method uses a specific body fat percentage formula based on your sex and measurements. For men: 495 / (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450. For women: 495 / (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450. All measurements are processed in centimetres to estimate your lean mass calculator results. This logarithmic transformation accounts for how different body sizes distribute adipose tissue.
Compared to the gold standard (DEXA scan), the Navy formula has a mean error of about ±3–4 percentage points. It is less accurate at very low or very high body fat levels, but reliable for tracking change over time.
Waist: at the narrowest point (usually just above the navel). Neck: below the larynx (Adam's apple), perpendicular to the spine. Hip (women only): at the widest point. Measure without compressing the skin for accurate fat mass calculator input.
American Council on Exercise categories: Essential fat is 2–5% (men) / 10–13% (women). Athlete: 6–13% / 14–20%. Fitness: 14–17% / 21–24%. Average: 18–24% / 25–31%. Obese: 25%+ / 32%+.
Body fat percentage is a more direct measure of adiposity than BMI, which can't distinguish muscle from fat. Use this body composition calculator to get a more nuanced view of your physical health.
Whether you're an athlete monitoring conditioning or just starting a fitness plan, this body fat calculator provides the data you need to adjust your training and nutrition. For a complete picture of your health metrics, check out the BMI Calculator and BMR Calculator. Bookmark this body fat calculator for regular check-ins on your body fat percentage progress.