Lean Body Mass Calculator
Everything you weigh that is not fat.
These formulas estimate from height and weight only — they cannot see how muscular you actually are. If you know your body fat percentage, weight × (1 − body fat ÷ 100) is more accurate than any of them.
Lean body mass (Boer)
56.0 kg
80.0% of body weight
How the Lean Body Mass Calculator works
Lean body mass is your weight minus your fat: muscle, bone, organs, blood and water. It matters more than scale weight for two reasons. It is what determines your resting metabolic rate, so preserving it is what keeps a diet working. And several drugs are dosed against lean mass rather than total weight, because fat tissue takes up far less of them.
Not medical advice. This calculator gives a general estimate, not medical advice. It cannot account for your individual health, medical history, or medication. Talk to a qualified healthcare professional before acting on any result.
Frequently asked questions
How is lean body mass calculated?
The Boer formula, the most widely used, is LBM = 0.407 × weight in kg + 0.267 × height in cm − 19.2 for men, and 0.252 × weight + 0.473 × height − 48.3 for women. It estimates from height and weight alone, so it cannot see how muscular you actually are.
Which lean body mass formula should I use?
Boer is the general-purpose default and the one most clinical references cite. James tends to read lower in heavier people. Hume was derived for drug dosing specifically. If you know your body fat percentage, skip all three — lean mass is simply weight × (1 − body fat ÷ 100), which is more accurate than any height-based estimate.
Why does lean body mass matter when losing weight?
Because lean tissue burns calories at rest and fat does not. Losing weight rapidly or without enough protein strips lean mass along with fat, which lowers your maintenance calories and makes the weight easier to regain. Resistance training and roughly 1.6–2.2 g of protein per kg of body weight are what protect it.
Is lean body mass the same as muscle mass?
No, and the difference is large. Lean body mass includes bone, organs, blood and the water in every tissue. Skeletal muscle is typically only about half of it. Someone with 60 kg of lean mass does not have 60 kg of muscle.