Estimate how much of your weight is muscle, bone, organs and water rather than fat.
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The formulas
| Formula | Men | Women |
|---|---|---|
| Boer (1984) | 0.407 × W + 0.267 × H − 19.2 | 0.252 × W + 0.473 × H − 48.3 |
| James (1976) | 1.1 × W − 128 × (W/H)² | 1.07 × W − 148 × (W/H)² |
| Hume (1966) | 0.32810 × W + 0.33929 × H − 29.5336 | 0.29569 × W + 0.41813 × H − 43.2933 |
W is weight in kg and H is height in cm. If you know your body fat percentage from a scan or smart scale, the tool also works out lean mass directly.
Why it’s useful
- Tracking lean mass shows whether you’re losing fat or muscle when you diet.
- Protein targets are sometimes based on lean mass.
- Some medicine doses are based on lean body weight; that’s for your doctor or pharmacist to work out.
Frequently asked questions
Which formula is best?
Boer is often used and works well for most adults. All three are estimates.
Is lean body mass the same as muscle?
No. It includes bone, organs and water as well as muscle.
How can I increase my lean mass?
Strength training and enough protein are the main ways.
Is anything stored?
No, it all runs in your browser.
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