Lean Body Mass Calculator: What You Weigh Besides Fat
Your weight is two numbers hiding in one: fat mass and everything else. Splitting them apart makes progress much easier to read.
What is the Lean Body Mass Calculator?
Lean body mass is everything that is not fat: muscle, bone, water, and organs. The Boer formula estimates it from weight and height with different coefficients for men and women, and subtracting it from total weight gives an estimate of fat mass. The result is general information only, not medical advice, and like all height-weight formulas it is an approximation, not a measurement.
How to use it
- Enter your weight in kilograms and height in centimetres.
- Select Male or Female.
- Read your lean body mass and estimated fat mass.
Worked example
A man weighing 80 kg at 180 cm has a lean body mass of 61.42 kg and an estimated fat mass of 18.58 kg (80 − 61.42).
What is lean body mass?
Lean body mass is your total weight minus your fat mass — muscle, bones, organs, and water combined. The Boer formula estimates it from height and weight alone, which makes it handy but approximate. If you are losing weight while lean mass stays steady, you are mostly losing fat, which is usually the goal.
Frequently asked questions
Why track lean mass instead of just weight?
Two people can weigh the same while one carries far more muscle; lean mass shows whether weight change is coming from muscle or fat.
Does gaining muscle raise lean mass?
Yes — strength training plus enough protein typically raises lean mass, which is why the scale alone can mislead during training.