Lean Body Mass Calculator
Estimate lean mass and fat mass from height and weight.
Results update as you type.
This calculator provides estimates based on population research. Results are not medical advice. Consult a qualified healthcare provider before making health or nutrition decisions.
How it works
Lean body mass is everything in your body that is not fat: muscle, bone, organs, connective tissue and the water they hold. A lean body mass calculator estimates that fat-free portion, which matters far more than total weight for judging fitness, strength potential and even certain drug doses that are targeted to lean tissue rather than overall size. This tool uses the Boer formula, one of the most widely cited equations for predicting lean mass from height, weight and sex, and it separates the scale reading into the part that is metabolically active and the part that is stored energy. Knowing your lean body mass helps you set smarter goals: during a fat-loss phase the aim is to shed fat mass while preserving lean mass, and a rising lean figure alongside steady weight often signals successful muscle gain that the scale alone would hide. Athletes and clinicians use a lean body mass calculator to scale protein needs, gauge body composition changes over time, and interpret strength relative to the tissue that produces it. Because the Boer equation is derived from population averages, it is an estimate rather than a lab measurement; methods like DEXA, hydrostatic weighing or bioelectrical impedance measure body composition more directly. Still, tracking the same formula over weeks gives a consistent, useful picture of how your body is changing, and it is a valuable complement to body-fat percentage and simple weight tracking.
Male LBM = 0.407×kg + 0.267×cm − 19.2; Female LBM = 0.252×kg + 0.473×cm − 48.3
The Boer formula predicts lean body mass as a weighted sum of body weight and height, with different coefficients for men and women that reflect their typical differences in muscle and fat distribution. Weight contributes because heavier bodies generally carry more of every tissue, while height contributes because taller frames hold more lean structure. Subtracting a constant calibrates the equation to real measured lean-mass data. Fat mass is then simply total weight minus the estimated lean mass.
Source:Boer P. (1984), American Journal of Physiology
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter weight, height and sex.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
Lean body mass updates instantly as you type — no button to press.
Frequently asked questions
What is a healthy lean body mass?
There is no single ideal figure because lean mass scales with height, frame and sex. Instead of a target number, watch the direction of change: preserving or increasing lean mass while losing fat is the goal for most people. Men typically carry proportionally more lean mass than women. Comparing your lean mass over time on the same formula is far more useful than chasing an absolute value someone else quotes.
How is lean body mass different from muscle mass?
Lean body mass includes all fat-free tissue: skeletal muscle plus bone, organs, skin, blood and body water. Muscle mass is only one component of it, usually a bit under half of lean mass in an average adult. So your muscle mass is always smaller than your lean body mass. Most formulas, including Boer, estimate total lean mass rather than muscle alone, because muscle is hard to isolate without imaging.
Which lean body mass formula is most accurate?
The Boer, James and Hume equations are the most commonly used, and Boer tends to perform well across a broad range of adults. All are population estimates, so none matches a direct measurement for a specific individual. For accuracy within a few percent, a DEXA scan, hydrostatic weighing or a Bod Pod is the reference standard. For everyday tracking, pick one formula and use it consistently rather than switching between them.
Why does lean body mass matter for drug dosing?
Some medications, particularly certain anaesthetics and chemotherapy agents, distribute mainly into lean tissue rather than fat. Dosing by total weight can then overdose people who carry more fat, so clinicians sometimes calculate doses from lean body mass or adjusted body weight instead. This is one reason a lean body mass calculator appears in clinical references, though any real dosing decision must be made by a qualified prescriber, not a general tool.
Can I increase my lean body mass?
Yes. Progressive resistance training combined with adequate protein, usually around 1.6 to 2.2 grams per kilogram of body weight for those building muscle, and sufficient overall calories and sleep, drives gains in lean mass over months. Older adults especially benefit, since strength training counters the natural age-related loss of muscle. Gains are gradual, so tracking lean mass every few weeks with the same formula shows progress the bathroom scale can mask.