Body Fat Calculator

How This Calculator Estimates Body Fat

This tool uses the U.S. Navy circumference method, a formula developed by the Naval Health Research Center that estimates body fat percentage from a few tape-measure readings rather than skinfold calipers or specialized equipment. For men, it uses neck and waist circumference along with height; for women, it adds a hip measurement, since fat distribution patterns differ by sex. The formula relies on the log-linear relationship between abdominal (and hip) girth and body density and is reasonably accurate for most adults, typically within about 3-4% of results from underwater weighing or DEXA scans.

Getting an Accurate Measurement

Measurement technique matters more than most people expect. Measure your neck just below the larynx (Adam's apple), your waist at the navel while relaxed (not sucked in), and — for women — your hips at their widest point. Use a flexible tape measure snug against the skin but not compressing it, and take each measurement two or three times to average out small errors, since a half-inch mistake on the waist can shift the estimated body fat percentage noticeably.

Body Fat Percentage Is Not the Whole Picture

Two people with identical body fat percentages can look and perform very differently depending on muscle distribution, so it's worth pairing this estimate with your BMI and lean body mass to get a fuller sense of your composition. This calculator provides an educational estimate only and is not a substitute for clinical body composition testing or medical advice — talk to a doctor or registered dietitian before making significant health or training decisions.