Lean Body Mass (LBM) Calculator
Estimate your lean body mass and body fat using the Boer formula, from your weight, height and gender.
Estimate based on the Boer formula; individual body composition varies.
What Is Lean Body Mass
Lean Body Mass, or LBM, is the weight of everything in your body except stored fat. It includes your muscles, bones, organs, water and connective tissue. A Lean Body Mass Calculator estimates this figure from your height, weight and sex, and from it works out your fat mass too.
Knowing your lean mass is useful for fitness and health. It helps you track whether changes in weight come from muscle or fat, set protein and calorie targets, and judge progress more clearly than the bathroom scale alone. This tool gives an estimate based on a formula, not a direct measurement, and it is not medical advice.
How It Works
This calculator uses the Boer formula, a well regarded equation that estimates lean mass from height and weight, with separate versions for men and women:
- Men: LBM = 0.407 times weight in kg, plus 0.267 times height in cm, minus 19.2.
- Women: LBM = 0.252 times weight in kg, plus 0.473 times height in cm, minus 48.3.
- Body fat mass = total weight minus lean body mass.
- Body fat percentage = fat mass divided by total weight, times 100.
The separate formulas reflect that men and women carry muscle and fat differently. Because the result is based on averages, it is an estimate rather than a precise scan.
Worked Example
Take a man who weighs 70 kg and stands 170 cm tall. Using the Boer formula: 0.407 times 70 = 28.49, plus 0.267 times 170 = 45.39, minus 19.2. Adding these gives 28.49 plus 45.39 minus 19.2 = 54.2 kg of lean body mass. His fat mass is 70 minus 54.2 = 15.8 kg, which is a body fat percentage of about 15.8 divided by 70, or roughly 22.6 percent. This is an estimate, not medical advice.
Using Lean Body Mass
Lean mass is a better progress marker than weight when you are training. If you lift weights and eat enough protein, your weight might stay flat while fat falls and muscle rises, a shift the scale hides but lean mass reveals. Many people also use LBM to set protein intake, often aiming for a target per kilogram of lean mass rather than total body weight.
In some clinical settings, lean mass guides drug dosing and nutrition planning, since it can predict metabolism better than total weight. Keep in mind that formula based estimates assume an average build, so very muscular or very lean people may see results that differ from a body composition scan such as DEXA. Use the figure as a helpful guide and confirm important decisions with a professional.
Frequently Asked Questions
Lean body mass is your total weight minus stored fat. It includes muscle, bone, organs, water and connective tissue. It is a useful measure of the non-fat part of your body.
The Boer formula estimates lean mass from height and weight, with separate equations for men and women. It is widely used because it is simple and reasonably accurate for people of average build.
Subtract your lean body mass from your total weight to get fat mass, then divide fat mass by total weight and multiply by 100 for body fat percentage.
No. Lean body mass includes muscle but also bone, organs and water. Muscle is only part of your lean mass, so the two figures are not the same.
The Boer formula gives a good estimate for average builds but assumes typical body composition. Very muscular or very lean people may get results that differ from a DEXA or other body composition scan.
No. This calculator provides a general estimate for fitness and information only. For clinical decisions or health concerns, consult a doctor or qualified professional.