Lean Body Mass Calculator
Enter your weight and body fat percentage to get lean body mass, fat mass and your FFMI — a height-normalized muscularity score.
Lean body mass
65.6 kg
Fat mass
14.4 kg
FFMI
20.8
FFMI guide (men): 18–19 average · 20–21 trained · 22–24 highly muscular · 25+ exceptional.
Formula
LBM = weight × (1 − bodyfat%) · FFMI = LBM/height(m)² + 6.1×(1.8 − height(m))How to use the Lean Body Mass Calculator
- 1Enter your body weight
- 2Enter your body fat percentage (use the Navy calculator to estimate it)
- 3Read LBM, fat mass and FFMI
Frequently Asked Questions
What is a good FFMI?
Average untrained men are ~18–19; well-trained naturals reach 22–24; above 25 is exceptional and rare without assistance.
Why track lean mass instead of weight?
On a diet or a bulk, the scale mixes fat and muscle changes. LBM tells you whether you're keeping the tissue you want.