Lean Body Mass Calculator

Lean body mass, or LBM, is defined as the difference between your total body weight and body fat weight. 

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Since high body fat percentage is associated with obesity, knowing and improving lean body mass is crucial to losing unhealthy, extra pounds. Lean body mass calculator is a useful tool available online that you can use to estimate your lean mass to gauge general health, as well as to achieve your fitness goals.

In this post, we explain how the lean body mass calculator works, what its variables are, and why knowing your lean body mass is medically important.

What Is Lean Body Mass?

Lean body mass (LBM) is the weight that comes from everything that makes up your body except fat. In simple words, lean mass is fat-free mass.

Lean Body Mass = Total Body Weight – Fat Weight

Thus, lean body mass calculator calculates weight from muscles, bones, ligaments, tendons, tissues, organs, and water.

However, it is important to mention that any change in lean body mass primarily occurs due to fluctuation in muscle strength and density, which is why the term lean muscle mass is often used interchangeably with body mass (LBM).

Lean Body Mass Equations

Here are the four different formulas used to calculate lean body mass:

The Boer Formula

The Boer formula gives the most accurate estimate and is therefore widely used to calculate lean body weight. This is the common formula used by the lean body mass calculator.

For Men

eLBM = (0.407 x weight in kg) + (0.267 x height in cm) – 19.2

eLBM denotes estimated lean body mass.

For Women

eLBM = (0.252 x weight in kg) + (0.473 x height in cm) – 48.3

The James Formula

For Men

eLBM = (1.07 x weight in kg) – {128 (weight in kg / height in cm)2}

For Women

eLBM = (1.07 x weight in kg) – {148 (weight in kg / height in cm)2}

The Hume Formula

For Men

eLBM = (0.32810 x weight in kg) + (0.33929 x height in cm) – 29.5336

For Women

eLBM = (0.29569 x weight in kg) + (0.41813 x height in cm) – 43.2933

Peter’s Formula

Body physiology and metabolism are different in kids, which is why a separate lean body mass formula has been devised for children.

eLBM = 3.8 x eECV

eECV, or estimated extracellular fluid volume, is the body fluid present outside the tissue cells.

eECV = 0.0215 x (weight in kg)0.6469 x (height in cm)0.7236

Variables Of Lean Body Mass LBM

Here are the factors that affect lean body mass:


Age is one of the most integral components of lean body mass. This is because your body composition changes with age.

As we grow old, muscle weight declines steadily after the age of 40. Since muscle density is directly related to lean mass, your LBM reduces with it too. This increases body fat percentage.


Body composition and body fat distribution are determined by gender. Men tend to have higher muscle mass and, by extension, lean mass. They also have a higher metabolic rate, which helps in the faster breakdown of body fat.

On the other hand, women comparatively have slower metabolism of fats and proteins and a higher body fat percentage. This implies decreased muscle mass and hence lower LBM.

Apart from body composition, body fat distribution is also different in men and women. Where women have more fat in gluteal-femoral region (hips and thighs), whereas, men tend to have body fat in abdomen. This affects the mass and strength of muscles.

Height and Body Weight

Body height and total body weight are also important when it comes to calculating lean body mass. A study shows a linear relationship between the speed of growth in height and the percentage increase in LBM.

The increase in bone density, muscles, and size of organs explains the linear relationship.

Importance Of Lean Body Weight

Maintaining adequate lean body weight is essential to health:

Increase Muscle Strength and Mobility

As we know, lean body mass is directly related to muscle weight. Therefore, if you work on improving your LBM, you naturally gain muscle strength.

Additionally, a rise in lean body mass also increases bone density. All of this helps with mobility.

Low Body Fat Percentage and Obesity Prevention

There are a number of ways in which lean body mass helps lose fat and prevent obesity.

It increases metabolism, which helps in the faster breakdown of fat tissue. Additionally, muscles require energy even at rest, which implies more calories are burned throughout the day. This decreases fat accumulation.

Increase Insulin Sensitivity

Fat free mass or lean body mass is involved in glucose uptake. Therefore, with high LBM, insulin sensitivity increases in the body.

This helps prevent diabetes and obesity. A study found a drop of 11% in insulin resistance with every 10% increase in muscle mass.

Increase Metabolic Efficiency

Muscle mass primarily comes from proteins. Proteins are important macronutrients, with a very high total daily energy expenditure TDEE. Therefore, with an increased lean body mass and high muscle percentage, your energy consumption and metabolism will naturally be high.

This helps with rapid and sustainable weight loss.

Increase Productivity

High metabolism implies a faster breakdown of nutrients and, thus, high energy production. This energy helps boost productivity.

Prevents Against Bone Diseases

As we age, bones become weak, and we are at a higher risk of developing osteoporosis, arthritis, and other related health complications.

An increase in lean body mass also results in an improvement of bone density and strength and thus helps prevent bone diseases.


Proteins (that make up the majority of muscles) are crucial for building and repairing damaged tissues, like skin, muscles, and other organs. Therefore, an increase in lean body mass plays a critical role in wound healing and in curing inflammatory diseases.

In cancer patients, the incidence of recurrence and mortality was found to be related to skeletal muscle loss.

Lean Body Mass From a Medical Point Of View

Using a lean body mass calculator is not as important for weight loss as it is for medical purposes.

As we know, an increase in LBM results in a high metabolic rate. This also leads to an increase in drug clearance.

Drug clearance refers to the ratio of the rate at which medicine is removed from plasma and the plasma concentration of the drug. This ratio is used to decide the dosage and frequency of medicine at the time of prescription.

In a lean person, a high dose might be required to ensure adequate drug effects.

How To Improve Lean Body Mass?

To improve your lean body mass, you need to have a healthy diet plan and an appropriate workout routine:

Diet Plan To Lose Body Fat and Increase Lean Body Mass LBM

When it comes to planning a diet to gain lean muscle, there are a couple of factors you should consider. These include:

  • Ideal body weight
  • Total daily energy expenditure
  • Basal Metabolic Rate
  • Body Fat Percentage

These three factors will help you decide your required calorie intake.

Ideal Body Weight

An ideal body weight calculator uses your age, sex, and height to estimate a healthy weight for you. This healthy weight comes from several prediction equations, of which body mass index BMI is the most reliable.

Body mass index is the ratio of your current weight (in kg) and height (in m2).

Your normal weight (falling in the healthy range according to the body mass index BMI scale) ensures the lowest risk of metabolic syndrome, heart disease, and early mortality, which is why maintaining it is crucial.

Total Daily Energy Expenditure TDEE

Total daily energy expenditure is the number of calories your body burns in a day. A TDEE calculator is used to estimate this energy expenditure. If you want to lose weight, your daily calorie intake just needs to be lower than your TDEE.

In contrast, if you want to gain weight, your calorie intake should be higher than TDEE. However, in doing so, fat intake should be minimal to prevent obesity.

Basal Metabolic Rate

Basal metabolic rate, or BMR, is the minimum calories you need for survival. In other words, it is the number of calories your body burns while you’re mentally and physically at rest.

Oftentimes, when planning a weight loss meal, people go all-in with very low-calorie diets, which can lead to calorie deficit (low energy). Understandably, your calorie intake should never fall below your basal metabolic rate, which is why using a BMR calculator is crucial.

It is essential to mention that in healthy adults, BMR is 60 to 70% of total daily energy expenditure.

Now, once you have an estimated value for TDEE, BMR, and ideal body weight in mind, it’s time to plan your diet.

Ideally, to gain muscle, your calorie intake should be 110% of TDEE. This 10% increase in TDEE is sufficient to help gain muscles without risking excess fat deposition.

Counting your macronutrients when deciding what to eat is an effective way to go about gaining lean body mass. Proteins, carbohydrates, and fats are considered macros, as they contribute the most to your calorie requirement.

Here’s how many calories a gram of each of these macros metabolizes into:

  • 1 gm of protein = 4 calories
  • 1 gm of carbs = 4 calories
  • 1 gm of fats = 9 calories

Ideally, 45 to 65% carbs, 10 to 35% protein, and 20 to 35% of healthy fats in diet is recommended. If you want to gain lean mass, you can increase the number of proteins.

However, before making any drastic changes in your diet, it is better to get an expert consultation to ensure you don’t consume unhealthy amounts of protein.

This is because excess proteins in the body are converted and stored as fats. Therefore, eating more proteins than required will have adverse effects on health and fitness, i.e., it will lead to obesity.

Moreover, in reducing fat content in diet, it is crucial to ensure you don’t lose essential body fat, as it can cause malabsorption of vitamins, and other health issues.

Physical Activity and Exercise

There are several hardcore exercises you can include in your workout routine to help in gaining muscle.

Strength training and engaging in isotonic and isometric exercises are mostly preferred.

Strength Training

Lifting weights, yoga, high intensity interval training (HIIT), and other bodyweight exercises can build stamina and and a leaner body.

If you cannot afford proper equipment required for these exercises, you can try small loads with more repetition, as they are at times as effective as intense weight lifting.

Isotonic Exercises

Isotonic exercise involves movements that build muscle resistance against motion. Over time, this leads to an increase in muscle length.

Following isotonic exercises help improve lean body weight:

  • Pushups
  • Squats
  • Crunches
  • Triceps dips

Isometric Exercises

Isometric exercises involve holding your body in one static position of stress for a long time. These exercises help build muscle strength.

  • Plank
  • Warrior pose
  • Wall sit
  • Glute bridge

These exercises are intense, and therefore, it is better to start with 30 seconds of holding time.

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