Inputs
Lean mass panelLean mass panel
Enter body weight and body fat percentage to estimate lean body mass, fat mass, and lean share.
Lean body mass is not the same as pure muscle. It includes muscle, bone, organs, and water, which is why scale weight can be misleading.
Lean body mass guide
What is lean body mass
Lean body mass is the portion of your weight that is not fat. It includes muscle, bone, organs, water, and other non-fat tissue, which is why it is broader than just muscle mass.
Comparison
Lean mass vs fat mass
Lean mass and fat mass are the two sides of body composition. When fat mass rises or falls, lean mass helps you understand what part of your body weight is still being carried by non-fat tissue.
Why it matters
Why scale weight is misleading
Two people can weigh the same and have very different body composition. One may carry more lean tissue while the other carries more fat, so scale weight alone can hide the real change.
Body fat context
Relation to body fat percentage
Lean body mass is derived from body weight and body fat percentage. If body fat goes down while weight stays stable, lean mass has usually improved relative to the total.
Muscle context
Muscle mass vs fat
People often say muscle mass when they really mean lean mass. Muscle is part of lean mass, but lean mass also includes bone, organs, and body water, so it is a broader and more useful estimate.
Training
How much muscle do I have?
This calculator cannot isolate pure muscle, but it gives a helpful estimate of the lean portion of body weight. That makes it easier to compare strength training progress with fat-loss or maintenance goals.
Limitations
When lean mass estimates are less precise
Lean body mass estimates depend on the body-fat number you enter. If the starting body-fat estimate changes, the lean mass result will change too, so trend tracking matters more than one-off readings.