Body Fat Percentage Calculator

Estimate your body fat percentage using the US Navy method. Determine your body composition category and fat vs lean mass.

This calculator estimates body fat two different ways and shows both so you can sanity-check them against each other. The headline number is the US Navy circumference method: for men it takes the logarithm of waist-minus-neck against the logarithm of height, and for women it adds the hip measurement into the girth term. Waist size is the dominant measurement for men — the girth term carries the largest coefficient and the widest real-world range — while for women the hip and waist contribute together. Two inputs on the form deliberately do not enter the Navy formula at all: your weight and age move the BMI-based comparison estimate (which is weight over height squared, adjusted for age and sex), but the Navy percentage is computed from tape measurements alone, so changing your weight will move fat mass and the BMI estimate while leaving the Navy percentage untouched. Fat mass and lean mass then split your total weight by the Navy percentage. Results are clamped to a 2-60 percent band, and an impossible tape pairing (waist smaller than neck) floors the girth term rather than erroring — expect a clipped reading, not a warning. Tape placement moves these numbers by several percent; for anything beyond estimation, a DEXA scan is the reference.