Lean Body Mass Calculator
The pounds of you that are not fat. Know this number and every diet decision after it gets easier.
Know it? Enter it for the accurate version. Do not know it? Leave it blank and the Boer formula estimates for you.
Fill in the fields above and your number appears here instantly.
What your numbers mean
Lean body mass
Muscle, bone, organs, and water. This is what burns calories at rest and what gives your body its shape at any weight.
Why protein gets set from this number
Protein targets scale with lean mass, not total weight. That is why a leaner person and a heavier person at the same scale weight need different amounts.
The only honest fat loss scoreboard
A diet that works drops fat mass and leaves lean mass alone. If lean mass is falling too, the deficit is too aggressive or protein is too low.
How to adjust after two weeks
- 1Weigh in the same way every morningAfter the bathroom, before food or water, same clothing. One day means nothing. The seven day average is the number you read.
- 2Compare week two's average to week one'sLosing fat: you want a half pound to one percent of bodyweight down per week. Building: a quarter to half pound up. Holding steady inside those ranges means the numbers are right, so leave them alone.
- 3Move calories, not everything at onceOff target for two straight weeks? Change calories by roughly 150 to 200 and hold protein exactly where it is. Protein is what protects the muscle you already built.
- 4Recheck the calculator when your weight moves 10 lbA lighter or heavier body burns a different amount. Ten pounds in either direction is the trigger to run these numbers again.
Numbers are the easy part.
Eating them every day is where people fall off. Turn these macros into a full 7 day meal and training plan, built around your body, free.
Start my free 7 day kickstartCommon questions
What is lean body mass?
Everything you are made of except fat: muscle, bone, organs, and water. It is the part of your bodyweight that does the work, and the part a smart diet is built to protect.
How do you calculate lean body mass?
If you know your body fat percentage, lean mass is simply bodyweight times one minus that percentage. If you do not, this calculator uses the Boer formula, which estimates it from height, weight, and sex.
Why does lean body mass matter for fat loss?
It sets your metabolism and your shape. Two people can lose the same 20 pounds and look completely different depending on how much of it was lean mass. Protein and resistance training are what decide which version you get.
What is FFMI?
Fat free mass index, your lean mass adjusted for height. Around 19 is untrained average for men, 22 to 23 is years of serious training, and 25 plus is exceptional. It is a far more useful muscle metric than BMI.
How much lean mass can I gain in a year?
A first year of hard, consistent training can add 15 to 20 pounds for men and 8 to 10 for women. After that it slows every year. Anyone promising faster is selling something.