Lean Body Mass Calculator

Calculate your lean body mass in pounds or kilograms by entering your sex, height, and weight.


Lean Body Mass:

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How to Calculate Lean Body Mass

Lean body mass (LBM) is an important component of your total body composition. This is a measure of your total body weight minus your total fat weight. So basically, your lean body mass accounts for the weight of your skeletal muscle mass, bones, and organs.

lean body mass = body weight – body fat

Formula showing that lean body mass is equal to body weight minus body fat.

The Most Accurate Way to Find LBM

The best way to get a direct measurement of lean body mass is through a DEXA scan (Dual X-Ray absorptiometry). A DEXA scan is often used to determine bone mineral density, however it also measures all components of your body composition.

It works by sending a low x-ray beam that calculates soft tissue, bone density, and body fat. This then gives an analysis of your body composition based on the density of your fat, muscle, and bone.[1]

While there are other methods to estimate body fat, such as underwater weighing and skinfold calipers, the analysis of body composition with DEXA is becoming more popular as this has the ability to evaluate lean body mass and fat mass with an accuracy that is close to that of CT and MRI.[1]

However, since many people do not have access to regular DEXA scans, formulas have been developed to get a rough estimate of lean body mass.

Lean Body Mass Formulas

There are several different formulas that have been developed to help estimate lean body mass.

Boer Formula

The Boer formula used body weight in kilograms and height in centimeters to estimate lean body mass. There are two different formulas for men and women.

For men:
LBM = (0.407 × weight [kg]) + (0.267 × height [cm]) − 19.2

For women:
LBM = (0.252 × weight [kg]) + (0.473 × height [cm]) − 48.3

Studies have found that the Boer formula should be the method of choice to calculate lean body mass in obese patients as it more closely estimates this value.[2]

James Formula

The James formula is one of the most widely used equations used in clinical practice to estimate lean body mass.[2] However, in obese patients, this formula reaches a plateau around a BMI of 37 in women and 43 in men. This makes other formulas, such as the Boer formula above, more appropriate in individuals with a BMI that places them in the obese II category.[3]

For men:
LBM (kg) = (1.1 × weight [kg]) – 128 × (weight [kg] ÷ height [cm])²

For women:
LBM (kg) = (1.07 × weight [kg]) – 148 × (weight [kg] ÷ height [cm])²

Hume Formula

Lean body mass can also be calculated using height and weight using the Hume formula.[4]

For men:
LBM = (0.32810 × weight [kg]) + (0.33929 × height [cm]) − 29.5336

For women:
LBM = (0.29569 × weight [kg]) + (0.41813 × height [cm]) − 43.2933

Lean body mass is an important health marker. Having a body composition with a higher percentage of lean body mass decreases the risk of chronic health conditions, such as cardiovascular disease.[5]

Understanding your body composition is oftentimes more important than just monitoring your overall body weight. For example, gaining muscle mass may make your overall weight increase, however gaining weight from muscle is healthier compared to if you gained body fat.

These lean body mass formulas can help you estimate your current lean body mass and monitor it over time.


  1. Messina, C., Albano, D., Gitto, S., Tofanelli, L., Bazzocchi, A., Ulivieri, F. M., Guglielmi, G., & Sconfienza, L. M., Body composition with dual energy X-ray absorptiometry: from basics to new tools, Quantitative Imaging in Medicine and Surgery, 2020, 10(8), 1687. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7378094/
  2. Caruso, D., De Santis, D., Rivosecchi, F., Zerunian, M., Panvini, N., Montesano, M., Biondi, T., Bellini, D., Rengo, M., & Laghi, A., Lean Body Weight-Tailored Iodinated Contrast Injection in Obese Patient: Boer versus James Formula, BioMed Research International, 2018, https://doi.org/10.1155/2018/8521893
  3. Nyman, U., James Lean Body Weight Formula Is Not Appropriate for Determining CT Contrast Media Dose in Patients with High Body Mass Index, Radiology, 2016, 278(3), 956-957. https://pubs.rsna.org/doi/full/10.1148/radiol.2016152031
  4. Hume, R., Prediction of lean body mass from height and weight, Journal of Clinical Pathology, 1966, 19,4, 389-91. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC473290/
  5. Lee, D. H., Keum, N., Hu, F. B., Orav, E. J., Rimm, E. B., Willett, W. C., & Giovannucci, E. L., Predicted lean body mass, fat mass, and all cause and cause specific mortality in men: prospective US cohort study, British Medical Journal, 2018, 362, https://www.bmj.com/content/362/bmj.k2575