Lean Body Mass Calculator

About this calculator

The Boer formula (1984) estimates lean body mass — everything in your body that isn't fat, including muscle, bone, organs and water — from just weight, height and sex, without needing calipers or a scan. For men: LBM = 0.407 × weight(kg) + 0.267 × height(cm) − 19.2. For women: LBM = 0.252 × weight(kg) + 0.473 × height(cm) − 48.3. Fat mass is simply total weight minus LBM.

It's widely used in clinical settings to dose medications that distribute through lean tissue rather than fat — anesthesia and certain chemotherapy drugs are calculated on lean body weight because dosing by total body weight can overdose people carrying extra fat mass. Strength coaches and physique athletes also track LBM over time as a better signal of muscle gain or loss than scale weight alone, since scale weight can't distinguish muscle gained from fat lost.

This calculator takes your weight, height and sex and returns your estimated lean body mass and fat mass side by side.