Lean Body Mass Calculator

What is Lean Body Mass (LBM)?

Lean Body Mass (LBM) is the total weight of your body minus all the weight due to fat mass. It includes the weight of your muscles, bones, organs, skin, and water. LBM is a more accurate indicator of your metabolic rate and overall health than total body weight alone. A higher LBM means you have more muscle mass, which burns more calories at rest. This LBM calculator uses the Boer formula, one of the most common estimation methods, to provide you with your Lean Body Mass and Body Fat Percentage. Tracking these numbers is far more valuable for assessing fitness progress than simply stepping on a scale.

Why LBM is a Better Metric Than Weight or BMI

While Body Mass Index (BMI) is a simple way to screen for weight categories, it has a major flaw: it doesn't distinguish between fat and muscle. An athlete with high muscle mass might be classified as "overweight" by a BMI Calculator, which can be misleading. LBM provides a much clearer picture:

• Tracks Muscle Growth: If you're strength training, you might gain muscle and lose fat simultaneously, and your total weight on the scale might not change much. Tracking LBM, however, will show you that your body composition is improving.
• Informs Caloric Needs: Your LBM is the primary driver of your Basal Metabolic Rate (BMR), the number of calories your body burns at rest. Knowing your LBM can help you more accurately determine your daily caloric needs for weight loss, maintenance, or muscle gain.
• Focuses on Health, Not Just Weight: A healthy body composition—more lean mass and less fat mass—is linked to a lower risk of chronic diseases. LBM shifts the focus from "weight loss" to "fat loss" and "muscle gain."

How This Calculator Works: The Boer Formula

This calculator uses a widely accepted formula developed by Dr. P. De Boer. It provides separate equations for men and women, using height and weight to estimate LBM. While it's an estimation and not as precise as a DEXA scan, it's one of the most accurate formula-based methods available for the general population. Once LBM is calculated, your Body Fat Mass and Body Fat Percentage are determined with simple arithmetic. For more in-depth health information, resources like Healthline offer detailed articles on body composition.