Lean Body Mass (Boer Formula) Calculator

About this calculator

The Boer formula (1984) estimates lean body mass — the weight of everything in your body except fat, including muscle, bone, organs, and water — from just height, weight, and sex, using separate linear equations for men and women. It was developed and validated against more precise body-composition measurement methods, and remains one of the more widely used lean-mass equations in clinical practice today.

Lean body mass matters because it's a better basis than total body weight for several clinical calculations, including certain medication dosing formulas, resting metabolic rate estimates, and tracking body-composition changes during weight loss or strength training (where the goal is usually to lose fat mass while preserving lean mass). This calculator applies the Boer equation to your inputs and also reports the implied fat mass — total weight minus the estimated lean mass.