Calculate your lean body mass from weight and body fat percentage. Free online lean mass calculator with formula, examples, and FAQ.
Lean body mass (LBM) is the weight of everything in your body except fat — including muscles, bones, organs, skin, and water. Knowing your lean mass is important for calculating appropriate medication dosages, determining nutritional needs, and tracking fitness progress. It is a more useful metric than total body weight for many health assessments.
Lean Mass = Weight × (1 - Body Fat% / 100)
Fat Mass = Weight × (Body Fat% / 100)Lean mass is simply your total weight minus the weight of your body fat. The body fat percentage tells you what proportion of your total weight is fat. Multiplying weight by (1 - body fat percentage/100) gives you the weight of all non-fat tissues in your body.
| Input | Output |
|---|---|
| Weight: 70 kg, Body Fat: 20% | Lean Mass: 56.0 kg, Fat Mass: 14.0 kg |
| Weight: 85 kg, Body Fat: 15% | Lean Mass: 72.3 kg, Fat Mass: 12.8 kg |
| Weight: 60 kg, Body Fat: 30% | Lean Mass: 42.0 kg, Fat Mass: 18.0 kg |