Lean Body Mass Calculator

What Is Lean Body Mass?

Lean body mass is your total weight minus your body fat. It includes muscle, bone, organs, and water, so it is larger than your muscle mass alone. Two people of the same weight can have very different lean mass, which is why this number is more useful than the scale when you are trying to change your body.

Lean Body Mass Formulas

If you know your body fat percentage, the calculation is direct:

Without it, researchers have estimated lean mass from height and weight. The three best known equations use weight (W) in kilograms and height (H) in centimeters.

Which Result Should You Use?

Use the body fat version when you have a reasonable estimate of your body fat. The height-and-weight formulas assume an average build, so they tend to miss for very muscular people. They were also built on different groups of people, which is why the three results can differ by a few kilograms.

For people with obesity, Boer is the safer of the three. The James equation levels off at high body weights and can give results that make no sense at the extreme end.

Lean Body Mass vs. Muscle Mass

These terms are often mixed up. Muscle is only part of your lean mass. Water, bone, and organs make up the rest, so day-to-day changes in hydration can move your lean mass estimate without any change in muscle.

What to Do With Your Number

• Track it over time. Take measurements under the same conditions each time, because one reading tells you little.
• Put it in context with the ffmi calculator, which adjusts lean mass for your height.
• Plan a fat loss phase around it with the body recomposition calculator.
• Compare your body fat against the body fat chart to see how you rank by age.

Frequently Asked Questions