Lean Body Mass (Hume Formula) Calculator

About this calculator

Lean body mass is total body weight minus fat mass — everything that isn't fat: muscle, bone, organs, and water. The Hume formula, published in 1966, is one of the classic equations for estimating it without specialized equipment, using just weight, height, and sex, with separate coefficients for men and women that reflect typical differences in body composition between the sexes.

Lean body mass matters clinically because many drug dosages — especially for anesthesia and chemotherapy — are calculated per kilogram of lean mass rather than total body weight, since fat tissue doesn't metabolize most drugs the same way lean tissue does. It's also used in sports science and body-composition tracking to separate muscle changes from fat changes. This calculator takes your weight, height, and sex and returns your estimated lean body mass using the Hume equation.