Body Fat Calculator
Estimate your body-fat percentage from simple tape measurements using the US Navy circumference method — no calipers or scales required. Choose metric or imperial units; the hip measurement appears when the female formula needs it.
Estimate body fat
Example: male, 175 cm, neck 37, waist 85 → 17.7%.
How the Navy method works
Developed for the US Navy's fitness program, the method fits body-fat percentage to a logarithmic function of circumference measurements and height: for men, 495 ÷ (1.0324 − 0.19077·log₁₀(waist − neck) + 0.15456·log₁₀(height)) − 450. The example figures above give 17.7%, computed at build time by the same tested engine the calculator uses. Its appeal is practicality — a tape measure beats a lab visit for tracking monthly trends.
Track trends, not single readings
Hydration, food timing, and tape placement can move a single estimate by a couple of percentage points. Measure under consistent conditions (same time of day, same landmarks), log the results, and judge the direction over weeks. Pair the trend with the BMI Calculator and how clothes fit for a fuller picture.
Frequently asked questions
How do I take the measurements?
Use a flexible tape, snug but not compressing the skin. Neck: just below the larynx, sloping slightly down to the front. Waist: at the navel for men, at the narrowest point for women. Hips (women): at the widest point. Measure two or three times and average.
How accurate is the Navy method?
Studies place it within roughly ±3–4% of laboratory methods like DEXA for most people — good enough to track trends, not good enough to obsess over single readings. Consistent technique matters more than the absolute number.
What are typical body-fat ranges?
Commonly cited adult reference bands: essential fat 2–5% (men) / 10–13% (women); athletes 6–13% / 14–20%; fitness 14–17% / 21–24%; average 18–24% / 25–31%. Bands vary by source and age.
Why does the female formula need a hip measurement?
Fat distribution differs by sex; the Navy regression for women was fitted with waist + hip − neck, which tracks their fat mass better than waist − neck alone.
Not medical advice: this is a general educational estimate from a published population formula and cannot assess your individual health. Consult a qualified healthcare professional for body-composition concerns. Measurements are processed locally in your browser and never transmitted. See the methodology page.