Lean Body Mass Calculator
Estimate lean mass and fat mass from total weight and body-fat percentage.
Inputs
Result
Lean body mass
64.0 kg
Fat mass 16 kg
Visual breakdown
Lean mass
64 kg
Fat mass
16 kg
Total weight
80 kg
Body fat
20%
Formula
Fat mass = weight × body fat % ÷ 100. Lean body mass = weight − fat mass.
Example
80 kg at 20% body fat → 16 kg fat + 64 kg lean mass.
Common examples
80 kg, 20% body fat
Lean mass 64 kg · fat mass 16 kg.
70 kg, 15% body fat
Lean mass 59.5 kg · fat mass 10.5 kg.
Tracking over time
Compare lean mass to spot strength training progress.
Frequently asked
Where do I get a body-fat number?
Try the Body Fat Calculator (US Navy method), a smart scale, DEXA, or skinfold calipers. Each method has its own accuracy range.
Why track lean mass?
Lean mass changes with strength training and rapid weight loss. Watching it alongside weight gives a fuller picture than scale weight alone.
Is this the same as muscle mass?
No — lean body mass includes muscle, bone, organs and water. It's a useful proxy but not pure muscle.
People also calculate
More health →Educational estimate only — accuracy depends on the body-fat measurement you start with.