Lean Body Mass Calculator
Three common anthropometric formulas — use the average as a ballpark.
Why lean body mass matters
Lean body mass drives metabolic rate, strength, and mobility. More lean mass means more calories burned at rest, better insulin sensitivity, and resistance to frailty as you age. Starting around age 30, adults lose 3–8% of muscle mass per decade without resistance training — a condition called sarcopenia.
Building lean mass requires three ingredients: progressive resistance training (2–4×/week), adequate protein (0.7–1g per lb bodyweight), and sufficient calories (slight surplus for growth, maintenance during fat loss). Cardio alone will preserve lean mass but rarely build it.
Frequently asked questions
Why does lean body mass matter?
Lean mass (muscle, organs, bone, water) determines your metabolic rate — more lean mass means more calories burned at rest. It's also the main predictor of strength, mobility, and fall prevention as you age. Sarcopenia (muscle loss with age) begins in the 30s and accelerates after 60 without resistance training.
How do I build more lean mass?
Resistance training 2–4x/week (compound lifts: squats, deadlifts, presses, rows) plus adequate protein (0.7–1g per lb bodyweight daily) plus a slight caloric surplus. Without the training stimulus, extra calories become fat. Without protein, you can't rebuild muscle fibers.
How much lean mass can I gain?
Newbie gains: 1–2 lb/month for the first 6–12 months of serious training. Intermediate: 0.5–1 lb/month. Advanced (5+ years): 2–6 lb/year total. Genetic ceiling for natural lifters is roughly height-100 lbs of lean mass (e.g., 5'10" = ~170 lb lean), give or take 10%.
Does cardio reduce lean mass?
Excessive cardio in a caloric deficit can. Moderate cardio (2–4 sessions/week, 20–40 min) combined with resistance training and adequate protein preserves muscle fine. Marathon volume (5+ hours/week) plus calorie deficit almost always costs some lean mass.
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