Body Fat Calculator
Estimate your body fat percentage from waist, neck, and height measurements.
Measurements
Body fat: %
How the US Navy formula works
The Navy method estimates body fat from a log-based formula using neck and waist circumference (plus hip for women) relative to height. It doesn't require any special equipment beyond a measuring tape, which is why it's been used for decades as a practical field method — though it's less precise than lab methods like DEXA scans or hydrostatic weighing.
Frequently asked questions
Where exactly should I measure waist and neck? Waist is typically measured at the navel (belly button) level, and neck just below the larynx (Adam's apple), with the tape horizontal and snug but not compressing the skin — measurement technique significantly affects accuracy.
Why do women need a hip measurement but men don't? The formula was derived separately for each sex from population data, and the female regression found hip circumference to be a statistically useful predictor of body fat alongside waist and neck, while the male formula did not need it.
How accurate is this compared to a DEXA scan? Less accurate — circumference-based methods typically have an error margin of a few percentage points compared to gold-standard methods like DEXA, but they're far more accessible and useful for tracking relative change over time.