Calculate lean body mass, fat-free mass, and muscle percentage. Measure body composition with Boer, James, and Hume formulas for accurate lean mass calculation. Track muscle gain, fat loss, and body recomposition with our free LBM calculator for fitness and health goals.
Calculate your muscle mass in 3 steps:
Input gender, age, weight, and height. Optional: add body fat % for most accurate calculation. All data processes using scientifically validated formulas.
Uses Boer, James, and Hume formulas - medical standards for lean body mass calculation. If body fat % provided, uses direct calculation method.
See lean mass, fat mass, muscle percentage, and category. Set muscle building goals and track progress over time for body recomposition.
Note: All formulas give estimates ±2-3 kg. Body fat % method is most accurate but requires knowing your body fat percentage (from DEXA, bod pod, or calipers). Formulas are best for tracking changes over time.
Everything except essential fat: muscles, bones, organs, water, connective tissue. Includes 2-5% essential fat (men) or 10-13% (women) needed for survival. LBM = Total Weight - Storage Fat.
EVERYTHING except ALL fat (including essential). Muscles, bones, organs, water minus all fat tissue. FFM = Total Weight - All Body Fat. Slightly lower than LBM by 2-13%.
Only voluntary muscles you can control and train (biceps, quads, abs). Excludes heart, organs, bones. Typically 40-50% of LBM. This is what you build through weight training!
Total Weight: 70 kg | Body Fat: 15% (10.5 kg)
LBM = 70 - 10.5 + 3.5 (essential fat) = 63 kg
FFM = 70 - 10.5 (all fat) = 59.5 kg
Skeletal Muscle = 63 × 0.45 = ~28 kg trainable muscle
Muscle burns 3× more calories than fat at rest. 1kg muscle = 13 kcal/day vs 1kg fat = 4.5 kcal/day. More LBM = higher BMR = easier weight maintenance.
Higher LBM = stronger, more powerful, better athletic performance. Muscle generates force for movement, sports, daily activities. Essential for quality of life as you age.
Muscle pulls on bones during training, stimulating bone growth. High LBM protects against osteoporosis, fractures, bone loss with aging. Especially important for women post-menopause.
High LBM reduces risk of diabetes, heart disease, metabolic syndrome. Muscle improves insulin sensitivity, glucose metabolism. Sarcopenia (muscle loss) linked to mortality.
Adults lose 3-8% muscle per decade after 30 if inactive. High LBM = independence, mobility, strength into old age. Resistance training preserves LBM regardless of age.
Scale weight lies! 70kg at 60kg LBM (lean) looks completely different than 70kg at 50kg LBM (high fat). Focus on building LBM, not just losing weight.
Lift heavy weights 3-5×/week. Focus on compound movements: squats, deadlifts, bench, rows. Increase weight/reps progressively. Muscle grows in response to mechanical tension and progressive challenge.
Eat 1.6-2.2g protein per kg body weight daily. Muscle needs amino acids to grow and repair. Distribute across 4-5 meals. Prioritize lean meats, fish, eggs, dairy, legumes, protein powder.
Eat 200-300 kcal above TDEE for muscle gain. Gain 0.25-0.5kg per week maximum. Faster = more fat gain. Track calories, protein, adjust weekly based on results.
Muscle grows during sleep, not training! Growth hormone peaks during deep sleep. Poor sleep = higher cortisol, less testosterone, muscle breakdown. Sleep = recovery = growth.
5g creatine monohydrate daily increases muscle mass 1-2kg in 8 weeks. Improves strength, power, workout performance. Most researched, safest muscle building supplement. Cheap and effective.
Measure LBM monthly, not weekly. Take photos, track strength (lift progression). Scale weight can mislead during recomp (losing fat + gaining muscle). Focus on LBM trend over 3-6 months.
Uses Boer, James, and Hume formulas - all medically validated. Averages results for most accurate lean mass estimate. Plus body fat % method if known.
See lean mass, fat mass, muscle percentage, and category. Visual chart shows exact body composition breakdown. Know exactly what you're made of!
Calculate target LBM for +5kg, +10kg muscle gain. See elite-level muscle mass potential (FFMI 25). Set realistic goals based on your height and frame.
Know if you have low, average, above average, or athletic muscle mass for your height. Compare yourself to population standards. Track improvement over time.
Switch between kg/cm and lbs/inches instantly. Perfect for global users from USA, UK, Europe, Asia, Australia. Universal fitness tracking.
Calculate LBM on any device. Track muscle gain at gym, home, or anywhere. Free, no signup required. Instant results!
Lean Body Mass (LBM) is total body weight minus storage fat, including muscles, bones, organs, water, and essential fat needed for survival (2-5% men, 10-13% women). LBM represents your "metabolically active" tissue. Example: 70kg person with 15% body fat has ~60kg LBM. Higher LBM = higher metabolism, more strength.
LBM formulas (Boer, James, Hume) are accurate ±2-3 kg for most people. Body fat % method is most accurate (±1 kg) if you know your true body fat percentage from DEXA, bod pod, or hydrostatic weighing. Use calculator for tracking changes over time, not absolute numbers. Monthly measurements show muscle gain/loss trends reliably.
LBM (Lean Body Mass) = Total Weight - Storage Fat (includes essential fat). FFM (Fat-Free Mass) = Total Weight - ALL Fat (no essential fat). LBM is slightly higher than FFM. Example: 70kg man, 15% body fat: LBM = 63kg (includes 3kg essential fat), FFM = 60kg (zero fat). Both track muscle gain equally well.
Beginners: 1-1.5kg muscle per month (year 1). Intermediate: 0.5-1kg per month (year 2). Advanced: 0.25-0.5kg per month (year 3+). Genetic limit: FFMI (Fat-Free Mass Index) of 25 for natural lifters. Women gain at 50-60% of male rates. Requires progressive overload, high protein (1.6-2.2g/kg), calorie surplus, consistency.
Yes, but only for: beginners (training <1 year), those returning after break, or obese individuals. Called "body recomposition." Requires: slight calorie deficit (TDEE -200 to -300), high protein (2g/kg), progressive strength training 4×/week. LBM stays same or increases slightly while fat mass drops. Advanced lifters must choose: bulk or cut.
Yes, sarcopenia (muscle loss) starts at 30. Sedentary adults lose 3-8% muscle per decade. By 80, can lose 40-50% of peak muscle mass! Solution: resistance training 2-3×/week maintains LBM at any age. Adults who lift weights have same LBM at 70 as sedentary 30-year-olds. Never too late to start!
Varies by gender and height. Men: Low <60kg, Average 60-70kg, Above Average 70-80kg, Athletic >80kg (for 175cm height). Women: Low <45kg, Average 45-55kg, Above Average 55-65kg, Athletic >65kg (for 165cm height). Calculate FFMI (FFM / height² in meters) - 18-20 is average, 22-24 is athletic, 25+ is elite natural lifter.
Body recomposition! Losing fat while gaining muscle simultaneously. Example: Lost 3kg fat + gained 3kg muscle = same scale weight but completely different body composition. This is why LBM matters more than weight! Focus on: measurements, photos, how clothes fit, strength gains, body fat %, LBM changes. Scale weight alone is meaningless.
