The lean body mass calculator splits weight and body fat % into LBM and fat mass (kg) for training and nutrition context.
How to use
- Enter weight (kg) and body fat (%).
- Read the stack visual and LBM vs fat mass.
- Estimate fat % with the body fat calculator; plan protein with the protein calculator.
Example
75 kg at 20% fat → ~60 kg LBM, ~15 kg fat.
Body fat measurement error flows straight into LBM.
Frequently asked questions
What is lean body mass?
Lean body mass (LBM) is total weight minus fat mass. Here: weight × (1 − body fat %), with fat mass = weight × body fat %.
Where does body fat % come from?
From scales, calipers, or the body fat calculator. Measurement error flows into LBM—use the same method for trends.
Vs BMI?
BMI ignores body composition; LBM with a known fat % approximates non-fat mass—useful with lifting and protein planning.
Use for protein targets?
Some coaches set protein from lean mass; estimate LBM here, then use the protein calculator or macros. Ask a pro whether lean-based protein fits you.
0% or 100% body fat?
Body fat must be 0–100% (not 100). Extremes are unrealistic—use a reasonable estimate if unsure.
Medical diagnosis?
No—fitness and nutrition math only, not diagnosis of muscle loss, edema, or disease.
Can I save weight and body fat?
Yes. Copy link below the form keeps your current inputs so you can share the scenario or save it for later.