Lean Body Mass Calculator

Lean body mass is everything that isn't fat — muscle, bone, organs, water. Estimate yours with the Boer formula, or compute it exactly if you know your body fat percentage.

How to use this calculator

Select your sex and enter height and weight.
If you know your body fat %, add it for an exact split; otherwise the Boer formula estimates it.
Press Calculate for lean mass, fat mass and a protein target scaled to LBM.

Formula used

Boer: men LBM = 0.407W + 0.267H − 19.2 · women 0.252W + 0.473H − 48.3

W in kg, H in cm. With a known body fat percentage the calculation is exact by definition: LBM = weight × (1 − BF%). Boer is also the formula behind many clinical LBM-based drug dose calculations.

Example calculation

Worked example

Male, 175 cm, 78 kg: Boer LBM = 0.407×78 + 0.267×175 − 19.2 = 31.7 + 46.7 − 19.2 = 59.3 kg, implying ~24% body fat.

If a DEXA scan says 18% instead: LBM = 78 × 0.82 = 64 kg — the measured number wins.

Why lean mass is the better anchor

Lean body mass drives your metabolism (muscle burns calories at rest), your strength potential, and how several drugs distribute — which is why clinicians and coaches both track it. Two people at 78 kg with 59 vs 68 kg lean look, perform and metabolize very differently despite identical scale weight.

It's also the honest scoreboard for body recomposition: losing 4 kg means little until you know whether it was fat or muscle. Tracking LBM (via consistent method) tells you whether a diet is working or just shrinking you.

Why use this calculator?

Anchor protein and calorie targets to lean mass, not total weight.
Judge diets by fat-vs-muscle change instead of scale weight alone.
Compare the formula estimate against scan results when you have them.

Frequently asked questions

What is a good lean body mass percentage?

Typical adult ranges: men ~75–85% of body weight lean (15–25% fat), women ~68–80% (20–32% fat), with athletes higher. The complement of your body fat percentage is your lean percentage.

Is lean body mass the same as muscle mass?

No — LBM includes bone, organs, skin and body water too. Skeletal muscle is roughly 40–50% of a fit person's LBM. That's why you can't gain 5 kg of LBM and call it all muscle.

How do I increase lean body mass?

Progressive resistance training, adequate protein (1.6–2.2 g/kg), and enough calories and sleep to recover. Realistic muscle gain is ~0.25–0.5 kg per month for women and 0.5–1 kg for men in the first training year, slowing after.