The Lean Body Mass Calculator computes a person's estimated lean body mass (LBM) based on body weight, height, gender, and age. For comparison purposes, the calculator provides the results of multiple formulas. 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. Multiple formulas have been developed for calculating estimated LBM (eLBM) and the calculator above provides the results for all of them. Lean Body Mass Formulas for Adults The Boer Formula:1 For males: eLBM = 0.407W + 0.267H - 19.2 For females: eLBM = 0.252W + 0.473H - 48.3 The James Formula:2 For males: eLBM = 1.1W - 128( W H )2 For females: eLBM = 1.07W - 148( W H )2 The Hume Formula:3 For males: eLBM = 0.32810W + 0.33929H - 29.5336 For females: eLBM = 0.29569W + 0.41813H - 43.2933 Lean Body Mass Formula for Children The Peters Formula:4 The author suggests that this formula is applicable for children aged 13-14 years old or younger. The formula is used to compute an eLBM based on an estimated extracellular volume (eECV) as follows: eECV = 0.0215·W0.6469·H0.7236 eLBM = 3.8·eECV In the formulas above, W is the body weight in kilogram and H is the body height in centimeter.