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 popular formulas.

It is similar to the Body Mass Index (BMI) calculator, Basal Metabolic Rate (BMR) calculator and the Body Fat Calculator because it calculates only one factor of your weight. However, it is different from other calculators due to the fact that it follows an entirely different formula and serves a different purpose.

Your lean body mass is the amount of weight you carry on your body that isn’t fat. The goal of any fitness enthusiast is to drop weight while keeping your lean body mass the same.

Lean body mass does not necessarily indicate fat-free mass. Lean body mass contains a small percentage of fat (roughly 3%) within the central nervous system (brain and spinal cord), the marrow of bones, and internal organs. It is measured in terms of density.

What is lean body mass?

A common misconception about lean body mass is that it equals a person’s ideal weight. However, the truth is that lean body mass is actually the sum of the weight of a person’s bones, muscles, organs, and blood-everything except for the fat. In other words, lean body mass has nothing to do with how “lean” a person would be if he/ she lost all that fat. In fact, it is impossible to stay alive without a minimal amount of fat in your body.

Why calculate lean body mass?

There is no concrete reason for calculating a person’s lean body mass since it does not tell a person how much weight they need to lose or gain. This calculator is mostly used by those who are curious to know how much they would weigh minus all the fat in their body.

Not a Substitute for Professional Help

Remember that the lean body mass calculator shows you only a part of your weight status. It is not a substitute for any guidance on weight loss. For ideas on how to lose or gain weight, it is best to get professional help. Your personal health trainer may take your BMI and Lean Body Mass into account but not rely on these factors entirely.

Difference Between BMI and Lean Body Mass

The BMI (Body Mass Index) of a person is calculated by taking into account the ratio of a person’s height and weight. It is used to calculate the amount of fat a person may have. BMI usually indicates whether a person is too thin or too fat based on their height weight ratio.

The lean body mass, on the other hand, is not used for fat reduction. It is only used to find out how much a person would weigh with 0% fat.


LBM is a part of body composition that is defined as the difference between total body weight and body fat weight. While the percentage of LBM is usually not computed, it is the complement of body fat percentage, and on average ranges between 60-90% of total body weight. Generally, men have a higher proportion of LBM than women do, and the dosages of some anesthetic agents, particularly water-soluble drugs, are routinely based on the LBM.