Work out muscle mass estimate instantly with clear inputs, formula shown and shareable results.
Lean body mass is everything that is not fat - muscle, bone, organs and water. Skeletal muscle is roughly 53% of that in adults, so an 80 kg person at 18% fat carries 65.6 kg lean and about 34.8 kg of skeletal muscle, 43% of body weight. The remainder is bone, organs and non-muscle water.
Lean body mass
LBM = weight x (1 - body fat / 100)
Skeletal muscle
SMM is about 0.53 x LBM in adults
These figures are population-average estimates, not a medical assessment or diagnosis. Body composition equations carry errors of several percentage points, and healthy ranges vary with age, ethnicity, muscularity and medical history. Discuss weight or body composition goals with a qualified clinician or dietitian.
No. Bone is about 15% of lean mass and organs another 20-25%, which is why muscle mass is always well below lean mass.
Roughly 0.5-1 kg a month for a novice trainee, falling to a few kilograms a year after the first couple of years.