Body Fat Calculator

About the Navy method

The U.S. Navy circumference method estimates body fat percentage from a few tape-measure readings — neck, waist, and (for women) hip — combined with height, using a logarithmic formula developed by the Naval Health Research Center. It doesn't require any special equipment beyond a tape measure, which makes it convenient for tracking trends over time, but clinical methods such as DEXA scans, hydrostatic weighing, or skinfold calipers measure body composition more directly and are considerably more accurate for a one-time reading.

Frequently asked questions

How accurate is this estimate?

The Navy method is generally accurate to within about 3-4 percentage points of more precise clinical methods for most body types, though it tends to be less reliable at the extremes (very lean or very high body fat) and doesn't account for individual differences in body shape.

Why does measurement technique matter so much?

Because the formula is sensitive to small errors: measuring the waist an inch too high or too low, or not keeping the tape level, can shift the result by several percentage points. Measure at the same spots each time for consistent trend tracking.

Is my data stored anywhere?

No — the calculation runs entirely in your browser; nothing you enter is uploaded or saved.