Body Fat Percentage Calculator
Estimate your body fat with the US Navy circumference method and the Deurenberg formula, side by side.
What is it
Body fat percentage is the share of your weight made of fat tissue. Two popular ways to estimate it without an expensive DEXA scan: the US Navy method plugs your waist, neck and height into a logarithm formula, while the Deurenberg formula converts your BMI and age into a rough fat estimate. Neither is lab-grade, but they agree surprisingly well for everyday tracking.
Notes & fun facts
The Navy method started as a cheap way to screen sailors aboard ships, where no one had room for a scanner. It works best when you measure at the same spot every morning — waist at the navel, neck just below the larynx. Relax the tape, don’t suck it in: honesty here beats a flattering number.
Origin & history
The US Naval Health Research Center published its circumference formulas in 1984 after years of comparing tape measures against underwater weighing. In 1991 Dutch researcher Paul Deurenberg showed that BMI plus age predicts body fat across populations with a simple linear equation, which is why BMI calculators still borrow it today.