Lean body mass (LBM) is a part of body composition that is defined as the difference between total body weight and body fat weight. This means that it counts the mass of all organs except body fat, including bones, muscles, blood, skin, and everything else. While the percentage of LBM is usually not computed, it on average ranges between 60-90% of total body weight. Generally, men have a higher proportion of LBM than women do. The dosages of some anesthetic agents, particularly water-soluble drugs, are routinely based on the LBM. Some medical exams also use the LBM values. For body fitness and routine daily life, people normally care more about body fat percentage than LBM. To compute body fat, consider using our body fat calculator or ideal weight calculator.