LBM & FFMI Calculator
Results are estimates only and may not reflect your individual needs. This tool is for educational purposes only and is not medical advice.
Calculate your lean body mass and fat-free mass index to assess your muscular development.
Your result will appear here
Enter your details and press Calculate LBM & FFMI.
Estimated result
FFMI above 25 is rare without performance-enhancing drugs. Results are estimates only.
Why use this calculator
FFMI (Fat-Free Mass Index) is a more accurate gauge of muscular development than BMI because it accounts for body fat. It shows how much lean mass you carry relative to your height — a useful metric for setting realistic physique goals and benchmarking progress.
How to use this calculator
Enter your sex, height, weight, and current body fat percentage. If you do not know your body fat %, use our Body Fat Calculator first. Press Calculate to see your LBM, FFMI, normalized FFMI, and muscular development category.
What the result means
LBM is your total weight minus estimated fat. FFMI is LBM divided by height squared (in metres). Normalized FFMI adjusts FFMI to a reference height of 1.80 m, enabling fair comparison between people of different heights.
Important limitations
FFMI is calculated from estimated body fat, which itself is an estimate. Small errors in body fat % can meaningfully shift the FFMI result.
FAQ
What is a natural FFMI ceiling?
Research suggests ~25 for men and ~21 for women as typical upper limits without performance-enhancing substances, though outliers exist.
How is FFMI different from BMI?
FFMI uses lean mass rather than total weight, making it more meaningful for athletes and muscular individuals.
These estimates are for educational purposes only and are not medical advice. They are not intended for children, teens, pregnancy, eating disorder recovery, or medical conditions.