Lean Body Mass Calculator

Estimate your lean body mass, everything that isn't fat, and your fat mass from height, weight, and sex using the Boer formula.

Lean body mass

60 kg

Fat mass—

Body fat—

Lean mass share—

Lean mass vs. fat mass

Your body composition split, based on the Boer estimate. Updates as you change the inputs.

How it works

Lean body mass (LBM) is your total weight minus body fat — muscle, bone, organs, and water. Knowing it helps with setting protein targets, dosing certain medications, and tracking muscle retention while losing fat.

The Boer formula

Men: LBM = 0.407·kg + 0.267·cm − 19.2
Women: LBM = 0.252·kg + 0.473·cm − 48.3

Fat mass is then your weight minus LBM, and body-fat percentage is fat mass divided by weight.

Frequently asked questions

Is lean body mass the same as muscle mass?

No. LBM includes muscle plus bone, organs, and body water. Skeletal muscle is only a portion of your lean mass.

Why estimate LBM instead of measuring it?

Direct measurement needs a DEXA scan or hydrostatic weighing. Formulas like Boer give a quick, no-equipment estimate that is good enough for everyday tracking.