Body Fat Calculator
Estimate body fat percentage using the U.S. Navy circumference method.
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How it works
This uses the U.S. Navy circumference method, which estimates body fat from a few tape measurements instead of calipers. For men it uses neck and waist; for women it adds hip. The measurements feed a logarithmic formula derived by the Navy to approximate body density, which is then converted to a fat percentage. Enter measurements in metric or imperial along with your height, and the tool returns an estimated body fat percentage and a general category. All math runs locally.
male % = 495 / (1.0324 − 0.19077·log10(waist−neck) + 0.15456·log10(height)) − 450
Common use cases
- Tracking body composition changes over time with just a tape measure.
- Getting a body fat estimate without calipers or a special scale.
- Pairing with BMI for a fuller picture than weight alone.
Frequently asked questions
How accurate is the Navy method?
It is typically within 3 to 4 percentage points of more precise methods like DEXA for most people, which is good for tracking trends. Accuracy depends on consistent, correct tape placement, so measure the same way each time.
Where do I measure?
Neck just below the larynx, waist at the navel for men and at the narrowest point for women, and hip at the widest point. Keep the tape snug but not compressing the skin, and stand relaxed.
Is this a diagnosis?
No. It is an estimate for general fitness tracking, not a medical assessment. Consult a professional for body-composition decisions related to health.