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Lean Muscle Mass Estimator

Enter your weight, height and sex to estimate lean body mass and skeletal muscle mass using the Boer formula.

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Lean Muscle Mass Estimator
Estimate lean body mass and fat mass using body measurements
♂ Male
♀ Female
Enter measurements to estimate muscle mass

Medical disclaimer. This calculator is provided for educational and informational purposes only and does not constitute medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional regarding your health, diet, exercise, or medication decisions. Read full disclaimer →

About Muscle Mass Calculator

Muscle mass (skeletal muscle mass) is calculated from total body weight, body fat percentage, and non-muscle lean mass (bone, organs, water). Our calculator uses the Lee formula: SMM = height^2 x (thigh circ x 0.031 + calf circ x 0.033 - age x 0.014 + sex constant). Alternatively, if BFP is known: Lean Mass = Weight x (1 - BFP), then subtract bone and organ mass estimates.

Average skeletal muscle mass as percentage of body weight: Men 38-54%, Women 28-39%. Muscle mass peaks in the late 20s and declines approximately 3-8% per decade after age 30 (sarcopenia), accelerating after 60. Resistance training 2-3 times per week is the most effective intervention to maintain and build muscle mass across all ages. Adequate protein intake (1.6-2.2g/kg) combined with progressive overload is the evidence-based approach for muscle hypertrophy.

Frequently Asked Questions

Lean body mass (LBM) is your total body weight minus fat mass - it includes muscle, bone, water and organs. This calculator uses the Boer formula, a well-established equation based on weight, height and sex: for men, LBM = 0.407 x weight(kg) + 0.267 x height(cm) - 19.2; for women, LBM = 0.252 x weight(kg) + 0.473 x height(cm) - 48.3.
Skeletal muscle is estimated at approximately 55% of lean body mass for most people. This calculator applies that ratio to your computed LBM to give an estimated skeletal muscle mass figure, alongside your estimated body fat percentage.
Average skeletal muscle mass as a percentage of body weight is roughly 38-54% for men and 28-39% for women. Muscle mass generally peaks in the late 20s and then declines about 3-8% per decade after age 30 - a process called sarcopenia - which accelerates further after age 60.
Resistance training 2-3 times per week is the most effective evidence-based intervention for maintaining and building muscle mass at any age. Combining this with adequate protein intake (roughly 1.6-2.2g per kg of body weight) and progressive overload - gradually increasing training demands - supports muscle hypertrophy.
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Related: Daily Protein Needs Calculator, Step Counter to Calories, All Health Tools