Lean Body Mass Calculator
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.
Result
The lean body mass based on different formulas:
Formula  Lean Body Mass  Body Fat 
Boer^{1}  53.3 kg (89%)  11% 
James^{2}  51.8 kg (86%)  14% 
Hume^{3}  51.2 kg (85%)  15% 
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 6090% of total body weight. Generally, men have a higher proportion of LBM than women do. The dosages of some anesthetic agents, particularly watersoluble 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:  
 
For females:  

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 1314 years old or younger. The formula is used to compute an eLBM based on an estimated extracellular volume (eECV) as follows:
eECV = 0.0215·W^{0.6469}·H^{0.7236} 
eLBM = 3.8·eECV 
In the formulas above, W is the body weight in kilogram and H is the body height in centimeter.
Lean Body Mass vs. Fat Free Mass
Lean body mass and fat free mass are often used interchangeably. While this is unlikely to cause issues in most cases, the two are not exactly the same.
Lean body mass includes the combined mass of bones, muscles, water, ligaments, tendons, and internal organs. Internal organs include some essential fat and the mass of this fat is included within the measurement of lean body mass. Although internal organs also have surrounding subcutaneous fat, this fat is not included within the measurement of lean body mass.
Fat free mass is calculated as the difference between total body mass and all fat mass including essential fat. This is the difference between fat free mass and lean body mass. Subtracting the mass of essential fat from lean body mass yields fat free mass. The difference between lean body mass and fat free mass amounts to approximately a 23% difference in men and 512% difference in women.
 Boer P. "Estimated lean body mass as an index for normalization of body fluid volumes in man." Am J Physiol 1984; 247: F6325
 James, W. "Research on obesity: a report of the DHSS/MRC group" HM Stationery Office 1976
 Hume, R "Prediction of lean body mass from height and weight.". J Clin Pathol. 1966 Jul; 19(4):38991.
 A. M. Peters, H. L. R. Snelling, D. M. Glass, N. J. Bird "Estimation of lean body mass in children". British Journal of Anaesthesia1 06(5): 71923 (2011).