Lean Body Mass Calculator
Estimate your Lean Body Mass (LBM) — the weight of everything in your body except fat. Useful for tracking muscle mass and setting fitness goals.
Computes estimated lean body mass (LBM) based on body weight, height, and gender using multiple published formulas (Boer, James, Hume). For children aged 14 or younger, the Peters formula is also provided.
About Lean Body Mass
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.
Lean Body Mass Formulas for Adults
The Boer Formula¹
Male: eLBM = 0.407W + 0.267H − 19.2
Female: eLBM = 0.252W + 0.473H − 48.3
The James Formula²
Male: eLBM = 1.1W − 128(W/H)²
Female: eLBM = 1.07W − 148(W/H)²
The Hume Formula³
Male: eLBM = 0.32810W + 0.33929H − 29.5336
Female: eLBM = 0.29569W + 0.41813H − 43.2933
W = body weight in kilograms; H = body height in centimeters.
Lean Body Mass Formula for Children
The Peters Formula⁴
Applicable for children aged 13–14 years old or younger. The formula first estimates extracellular volume (eECV):
eECV = 0.0215 · W0.6469 · H0.7236
eLBM = 3.8 · eECV
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 — including essential fat within those organs. Fat free mass is calculated as the difference between total body mass and all fat mass including essential fat. The difference between lean body mass and fat free mass amounts to approximately 2–3% in men and 5–12% in women.
References
- Boer P. "Estimated lean body mass as an index for normalization of body fluid volumes in man." Am J Physiol 1984; 247: F632-5.
- 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):389-91.
- A. M. Peters et al. "Estimation of lean body mass in children." British Journal of Anaesthesia 106(5): 719-23 (2011).