How To Calculate Lean Body Mass

calculate lean body mass

What Is Lean Body Mass?

Your Lean Body Mass (LBM) is the amount of weight you carry on your body that isn’t fat. If you weigh 100kg but you’re 30% fat, then your Lean Body Mass will be around 70kg.

Why measure it? Muscle burns more calories than fat. The higher your LBM, the more calories you’ll need. The lower your LBM, the fewer calories you’ll need. This could be why an obese person over-estimates how much they need to eat and why a muscular person under-estimates how many extra calories they need to gain lean muscle.

Part 1 – Calculating Lean Body Mass

I’m going to show you how to judge your body fat percentage accurately enough to set your nutritional needs, for ways to get a more accurate reading click here. Your body fat percentage is the proportion of your entire body-weight that is fat.

Scan through the pictures below to find the best approximation of your body fat levels. Remember, this could be somewhere in-between two images.

Note: there is a level of ‘essential fat’ for your physiological health, which is around 5% for men and 10% for women. It is not recommended you are below this level for an extended period of time.

body fat percentage women chart
A Note On Body Dysmorphia

Body Dysmorphia is an anxiety disorder related to body image. Generally in the form of obsessive worrying about perceived flaws in your physical appearance. We are not here to fuel this issue.

For a woman, 11-12% fat should not be the goal. For a man, the goal is not 3-4% fat. These physiques represent a 24-48 hour window of extreme leanness created through dehydration and carbohydrate manipulation in order to be photogenic. Even the women in the 14-15% range (6-7% for men) seen in magazines have likely got themselves “photo-shoot ready” with carb cycling and most do not look like this every day.

Athletic Women have 14-20% Body Fat.

Athletic Men have 7-13% Body Fat

I Have My Body Fat Percentage, Now What?

Now enter your current weight in kilograms (kg) to the calculator below, along with your estimated body fat %.

If you only know your weight in pounds (lbs) you will need to enter that and check the Convert lbs to kg output for your weight in kilograms.

You now have an estimate for your Lean Body Mass (kg). If you wish to use this to calculate your calorie needs then carry on to Part 2.

About Fraser_9to5 241 Articles
Site owner. I'm a graduate in Sports Science and have an MSc in Sports Biomechanics. I set up 9to5strength in 2015 as a resource for people interested in strength training, nutrition and fitness. I consider myself a fitness blogger and enjoy creating YouTube videos and trying out workout programs.