Skeletal muscle mass is the most metabolically important component of your body composition. It drives strength, metabolism, glucose tolerance, and longevity. Our muscle mass calculator implements the Lee 2000 anthropometric equation, the most widely cited formula for estimating skeletal muscle mass from height, weight, age, and sex without requiring DEXA scanning. It also computes the Skeletal Muscle Mass Index (SMM/height²) and screens against AWGS 2019 sarcopenia cutoffs (men <7.0 kg/m², women <5.7 kg/m²).
Input weight (kg), height (cm), age, and sex.
If known, enter body fat percentage for additional context.
See your estimated skeletal muscle mass in kg and as a percentage.
Compare your SMI against the sarcopenia cutoffs.
The Lee 2000 equation was developed against MRI-measured skeletal muscle mass and validated across multiple populations. It provides a clinically useful estimate without imaging. The Skeletal Muscle Mass Index (SMI) normalizes for height and is the basis for sarcopenia screening — the Asian Working Group for Sarcopenia (AWGS) 2019 uses cutoffs of <7.0 kg/m² for men and <5.7 kg/m² for women.
SMM = 0.244 × W + 7.8 × H(m) + 6.6 × sex − 0.098 × age − 3.3
AWGS 2019 sarcopenia cutoffs: men SMI <7.0 kg/m², women <5.7 kg/m²
Skeletal muscle is roughly 40-45% of body weight in healthy young adults
Muscle mass declines ~3-8% per decade after age 30 if not actively maintained
Resistance training preserves and builds skeletal muscle at any age
Adequate protein (1.2-2.0 g/kg) and resistance training are the two most effective interventions
DEXA, BIA, and ultrasound are more accurate than anthropometric estimates
Sarcopenia is independently associated with falls, fractures, hospitalization, and mortality
Skeletal muscle mass is a critical biomarker for health, fitness, and longevity. It constitutes approximately 30-40% of total body weight in healthy adults — roughly 20-24 kg for an average man and 15-18 kg for an average woman. Muscle mass drives basal metabolic rate (each kilogram of muscle burns approximately 13 calories per day at rest, compared to just 4.5 for fat), supports joint stability, regulates blood glucose by serving as the primary site for insulin-mediated glucose disposal, and is independently associated with lower all-cause mortality. After age 30, muscle mass declines at roughly 3-8% per decade if no resistance training is performed, accelerating after age 60. When muscle mass drops below clinical thresholds, the condition is called sarcopenia — defined by the Asian Working Group for Sarcopenia (AWGS 2019) as a skeletal muscle mass index (SMI) below 7.0 kg/m² for men or 5.7 kg/m² for women. Sarcopenia affects an estimated 10-16% of adults over 60 worldwide and dramatically increases fall risk, hospitalization rates, and mortality. While DEXA scanning is the gold standard for measuring muscle mass, the Lee 2000 anthropometric equation provides a validated estimate using just height, weight, age, and sex, making it accessible for screening outside clinical settings.
Skeletal muscle is your largest organ system by mass, your biggest glucose disposal site, and the dominant determinant of resting metabolic rate. Maintaining muscle mass into older age is one of the most reliable predictors of healthy aging — it correlates with lower disability rates, fewer falls, less type 2 diabetes, and longer life. Resistance training and adequate protein are the two interventions with the strongest evidence.
Sarcopenia is silent until it isn't — most adults don't notice gradual muscle loss until they fall, fracture a hip, or struggle with stairs. Screening with SMI lets you catch the problem early when interventions still work well. After age 50, getting an annual or biennial body composition check (DEXA, BIA, or anthropometric estimate) is one of the highest-yield preventive health practices available.
Data sourced from trusted institutions
All formulas verified against official standards.