What is lean body mass?

Lean body mass is your total bodyweight minus your fat mass. It includes muscle, bone, organs, skin, and body water. It is the metabolically active part of your body, which is why many nutrition and training targets are based on it rather than on total weight.

How is lean body mass calculated?

If you know your body fat percentage, lean mass is your weight multiplied by one minus that percentage. A person weighing 80 kilograms at 15 percent body fat carries 68 kilograms of lean mass and 12 kilograms of fat. Without a body fat value, formulas like the Boer formula estimate it from sex, height, and weight.

What is the Boer formula?

The Boer formula estimates lean body mass from sex, height, and weight alone. For men it is 0.407 times weight in kilograms plus 0.267 times height in centimeters minus 19.2. For women it is 0.252 times weight plus 0.473 times height minus 48.3. It is widely used in clinical settings when no body fat measurement is available.

What is a good lean body mass percentage?

Most healthy men carry roughly 75 to 90 percent of their bodyweight as lean mass, and most healthy women roughly 68 to 80 percent, since women naturally carry more essential fat. Athletes sit near the top of those ranges. Higher is not always better: a certain amount of body fat is essential for health.

Is lean body mass the same as muscle mass?

No. Muscle is only one part of lean body mass, typically around 40 to 55 percent of it. Bone, organs, and water make up the rest. Lean mass can rise from water retention or stored glycogen without any new muscle, so treat short-term jumps with caution and watch the trend instead.

How do I increase lean body mass?

Progressive strength training combined with enough protein, roughly 1.6 to 2.2 grams per kilogram of bodyweight per day, and a small calorie surplus is the proven route. Recheck your lean mass every few weeks rather than daily, because water swings mask the real trend.

Free lean body mass calculator

Know what your weight
is actually made of.

Split your bodyweight into lean mass and fat mass, from your body fat percentage or the Boer formula. Free, instant, no signup.

Sex

Units

WeightkgBody fat%

Heightcm

Body fat is optional. Not sure of yours? The body fat calculator estimates it in seconds.

Your lean body mass

60.9kg

Boer formula estimate

76% of your bodyweight is lean tissue.

Estimated with the Boer formula from your sex, height, and weight. Enter a body fat percentage for a result based on your own measurement.

Fat mass: 19.1 kg
Lean percentage: 76%

Lean body mass covers muscle, bone, organs, and water, so it is bigger than muscle alone. To see how your lean mass compares to the natural muscle ceiling, try the FFMI calculator.

Your lean body mass

60.9 kg That number is the input.

Where the muscle goes is the output. See it with a free physique scan.

Free physique scan

How to calculate your lean body mass

Enter your sex, height, and weight, then add a body fat percentage if you know it, to split your bodyweight into lean mass and fat mass.

1
Enter your sex, height, and weight
Choose male or female, then provide your height and bodyweight in metric or imperial units.
2
Add your body fat percentage if you know it
With a body fat value the calculator measures your lean mass directly. Leave it empty and the Boer formula estimates it from your height and weight.
3
Read your result
See your lean body mass, your fat mass, and the percentage of your bodyweight that is lean tissue.

What the number means

The scale weighs everything. Lean mass is the part that trains.

More than muscle

Lean body mass is everything that is not fat: muscle, bone, organs, and water. Muscle is the part you can grow, but it usually makes up only around half of your lean mass.

The number worth tracking

Bodyweight alone hides what is changing. When your weight moves, comparing lean mass and fat mass tells you whether you gained muscle, lost fat, or both at once.

What gets built on it

Protein targets, calorie needs, and many clinical doses are set from lean mass rather than total weight, because fat tissue burns far less energy than lean tissue.

Questions, answered

Lean body mass, explained.

What is lean body mass?: Lean body mass is your total bodyweight minus your fat mass. It includes muscle, bone, organs, skin, and body water. It is the metabolically active part of your body, which is why many nutrition and training targets are based on it rather than on total weight.
How is lean body mass calculated?: If you know your body fat percentage, lean mass is your weight multiplied by one minus that percentage. A person weighing 80 kilograms at 15 percent body fat carries 68 kilograms of lean mass and 12 kilograms of fat. Without a body fat value, formulas like the Boer formula estimate it from sex, height, and weight.
What is the Boer formula?: The Boer formula estimates lean body mass from sex, height, and weight alone. For men it is 0.407 times weight in kilograms plus 0.267 times height in centimeters minus 19.2. For women it is 0.252 times weight plus 0.473 times height minus 48.3. It is widely used in clinical settings when no body fat measurement is available.
What is a good lean body mass percentage?: Most healthy men carry roughly 75 to 90 percent of their bodyweight as lean mass, and most healthy women roughly 68 to 80 percent, since women naturally carry more essential fat. Athletes sit near the top of those ranges. Higher is not always better: a certain amount of body fat is essential for health.
Is lean body mass the same as muscle mass?: No. Muscle is only one part of lean body mass, typically around 40 to 55 percent of it. Bone, organs, and water make up the rest. Lean mass can rise from water retention or stored glycogen without any new muscle, so treat short-term jumps with caution and watch the trend instead.
How do I increase lean body mass?: Progressive strength training combined with enough protein, roughly 1.6 to 2.2 grams per kilogram of bodyweight per day, and a small calorie surplus is the proven route. Recheck your lean mass every few weeks rather than daily, because water swings mask the real trend.

See where your lean mass actually sits.

Lean mass is one number. The physique rater scores every muscle group from photos and finds your weak points.

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Know what your weightis actually made of.