Lean body mass calculator
Everything that isn’t fat. Enter height and weight for three formula estimates, or add your body fat percentage for the direct number.
Enter your height and weight.
Lean body mass formulas
Weight in kg, height in cm:
| Formula | Men | Women |
|---|---|---|
| Boer | 0.407W + 0.267H − 19.2 | 0.252W + 0.473H − 48.3 |
| James | 1.1W − 128(W/H)² | 1.07W − 148(W/H)² |
| Hume | 0.32810W + 0.33929H − 29.5336 | 0.29569W + 0.41813H − 43.2933 |
These formulas estimate from size alone, so they miss muscle you’ve built. If you lift, get a body-fat figure from the Navy tape method and use that line instead. Then check your FFMI to see how muscular that lean mass is for your height.
Questions people ask
What is lean body mass?
Lean body mass (LBM) is your total weight minus fat: muscle, bone, organs, skin and water. It is the part of you that a good transformation tries to keep or grow while fat comes down.
Which lean body mass formula is most accurate?
If you know your body-fat percentage from a DEXA scan or careful tape measurements, weight × (1 − body fat) beats any height-and-weight formula. Without it, the Boer formula (1984) is generally the best all-round estimate for adults; James and Hume are shown for comparison.
Why do the formulas give different answers?
Boer, James and Hume were fitted to different study groups using only height and weight. They cannot tell a muscular person from a heavier one of the same size, so they diverge most for lifters and for people with obesity.
What lean body mass percentage is healthy?
It is simply 100 minus body fat %. For men, around 75–86% lean (14–25% fat) covers fitness to average; for women around 68–79% lean (21–32% fat).