Lean Body Mass Calculator

Pro tips most people learn the hard way

• After age 30, you lose 3 to 8 percent of muscle per decade unless you fight back with strength training. This is sarcopenia and it's accelerating in your 60s and beyond. The fix isn't supplements — it's lifting weights 2 to 3 times a week plus eating 1.6 grams of protein per kilo of bodyweight, sustained for life.
• Lean body mass is not the same as muscle mass — only about half of LBM is actually skeletal muscle. The rest is bone, organs, connective tissue, and body water. For general health and fitness planning, LBM is the practical metric; for bodybuilding-level tracking, you need DEXA or BIA to isolate skeletal muscle specifically.
• Beginners can realistically gain 0.25 to 0.5 kg of muscle per month with proper training and protein. Experienced lifters slow to 0.1 to 0.2 kg per month. Anything faster than this on a natural training plan is almost certainly water weight, glycogen storage, or wishful tracking — not actual new muscle.
• Track LBM monthly, not weekly. Real composition change is slow and weekly readings are mostly noise — water retention, glycogen, last meal volume. Combine the formula with monthly tape measurements (waist, chest, arms) and progress photos in the same lighting and pose for an honest picture.
• Women carry roughly 10 to 15 percent less LBM than men at the same height and weight — biology, not training quality. This is also why women generally need higher essential body fat (10 to 13 percent vs 2 to 5 percent for men) for hormonal and reproductive health. Don't compare absolute numbers across sexes; track your own trend.