Lean Body Mass Calculator

Lean body mass (LBM) is the weight of everything in your body that isn't fat — muscle, bone, organs, connective tissue, and water. Your total body weight is simply your lean mass plus your fat mass, so knowing one tells you about the other.

LBM is a useful reference point when you're changing your body. During weight loss the goal is usually to lose fat while preserving lean mass; during training the goal may be to add lean mass. Tracking LBM alongside weight gives a fuller picture than the scale alone.

This is an estimate from height, weight, and sex — not a direct measurement. It's a reasonable ballpark and good for tracking trends, but for a precise figure you'd want a body-composition method such as a DEXA scan or the circumference-based Body Fat calculator, from which lean mass follows directly.

Formula. We use the Boer equation. 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. Imperial input is converted first, and the result is shown in the weight unit you're using.

Source. The Boer formula was published in the American Journal of Physiology in 1984 and is a widely used height/weight-based estimate of lean body mass. Alternatives such as the Hume and James equations exist and give slightly different numbers.

Confidence. We label LBM moderate confidence: it's a sound approximation from three inputs, but it doesn't measure your body composition directly, so treat it as an estimate — most valuable for watching change over time rather than as an exact figure.