Lean Body Mass Calculator
Lean body mass is everything you weigh that is not fat: muscle, bone, organs, blood and the water in all of it. It is the part of you that burns calories at rest, and the part a good training block adds to and a bad diet takes from.
If you know your body fat percentage, enter it and get exact numbers. If you do not, three published equations estimate it from height and weight and show you how far apart they land. These are estimates, not medical measurements. Want to know your body fat first? Use the Body Fat Calculator, then see how much muscle that leaves with the FFMI Calculator.
Feminine
Masculine
Your lean body mass
176.0 lb at 18% body fat leaves 31.7 lb of fat
31.7 lb fat mass
Your weight minus your lean mass
82% of your weight
Lean mass is a share of the scale, not a goal weight
18.0% body fat
The figure you entered
Resting burn
The Katch-McArdle equation puts your BMR at about 1,784 kcal a day (370 + 21.6 x lean kg). Work out the rest of your day with the BMR Calculator and TDEE Calculator.
Protein target
Muscle gain from training levels off around 1.6 g of protein per kg of body weight. People carrying a lot of fat often apply that range to lean mass instead, which here is 105 to 144 g a day (1.6 to 2.2 g per lean kg). That is a common convention, not a trial result.
Your lean mass is only as good as the body fat number behind it. A body scan reads one to three photos and returns body fat with a range, plus lean mass and FFMI. Your first scan is free with an account.
Get your body scanYou know your body fat %
Then this is arithmetic, not an estimate: lean mass is weight times (1 minus body fat). It is exactly as good as the body fat number you put in. A DEXA scan or a body scan is a sturdier source than a bathroom scale that reads body fat. No number yet? Try the Navy method in the Body Fat Calculator.
You do not
Boer, James and Hume predict lean mass from height and weight alone [1][2][3]. They are the formulas clinicians use when nobody has measured anything. The price is that they treat everyone of your height and weight as the same body, so a lifter and a desk worker get the same answer.
Why three equations
Each was fitted to a different group at a different time, so they disagree by a few kilograms. James curves with build and becomes unreliable at very high and very low BMI [4]. Hume came from 29 men and 27 women in 1966 [3]. When all three land close together, trust the cluster. When they spread, that spread is the honest margin.
Three jobs, in the order most people need them.
1. Your resting burn
The Katch-McArdle equation is the one BMR formula built on lean mass: 370 plus 21.6 per kilogram [5]. Because it uses lean mass rather than weight, it is the one to reach for once you know your body fat. Put it to work in the BMR Calculator, then scale it to a real day in the TDEE Calculator.
2. A protein target
Across 49 trials, the extra muscle from protein flattened out around 1.6 g per kg of body weight [6]. Basing the same range on lean mass is a common way to avoid over-eating protein at a higher body fat. It is a convention, not a trial result, so treat it as a sensible starting range.
3. A better scoreboard
Body weight alone cannot tell fat lost from muscle lost. Track lean mass alongside it during a cut: if weight falls while lean mass holds, the diet is working. If both fall, eat more protein, lift heavier and slow the cut.
Take two men who are both 180 cm and 80 kg. One lifts four days a week and the other has not exercised in a decade. The equations give them the same lean mass, because the inputs are the same. Compare the implied body fat on this page with your mirror: if you train, the real answer is probably more lean mass than the equations say, and if you do not, probably less. That gap is the reason to measure body fat directly when it matters.