Body Fat Percentage Calculator

The US Navy method estimates body fat from a few tape measurements instead of calipers. It is repeatable and free, but it reads shape rather than tissue, so it can be several percentage points off for very lean or very muscular people.

Body fat percentage is the share of your total weight that is fat tissue, and unlike BMI it separates fat from muscle. This calculator uses the US Navy circumference method, developed by Hodgdon and Beckett at the Naval Health Research Center in 1984. It estimates body density from a handful of tape-measure readings — neck, waist, height, and for women the hips — and converts that density into a percentage. The constants come from a regression against personnel whose body fat was measured by underwater weighing, which is why they look arbitrary: they are fitted numbers, not physical quantities. Read the result against the American Council on Exercise reference ranges, where the fitness band sits at roughly 14 to 18 percent for men and 21 to 25 percent for women. Those are population benchmarks, not disease thresholds. Below the fitness band lies essential fat, the minimum needed for hormone regulation and organ protection, and dropping under it is dangerous rather than impressive. The caveat that matters most is precision. The method carries a typical error of three to four percentage points against a DEXA scan, and your own measuring adds to that: a single centimetre off at the waist moves the answer by half a point to a full point. Measure twice, take the average, and use the number to track a direction over months rather than to settle a question today.