Fat-Free Mass Index (FFMi): -
Are you gaining muscle or just adding fat? The Fat-Free Mass Index (FFMI) gives you a more accurate picture of your muscular development by removing fat from the equation. The FFMI Calculator is ideal for fitness enthusiasts, athletes, and bodybuilders who want to track lean muscle mass relative to their height.
At Calculators.at, our free FFMI Calculator offers a fast and simple way to assess your lean body mass potential and compare your physique to standardized values.
Fat-Free Mass Index (FFMI) measures the amount of lean mass (muscles, bones, organs, and water) you have in relation to your height. It improves upon BMI (Body Mass Index) by factoring out body fat and focusing on muscle mass.
FFMI = (Lean Body Mass in kg) / (Height in meters)²
If you know your body fat percentage, you can calculate lean body mass as:
Lean Mass = Total Body Weight × (1 − Body Fat %)
Then plug it into the FFMI formula.
Input the following:
The calculator will automatically compute your FFMI score and give a quick interpretation.
FFMI Value Classification < 18 Below average 18 – 20 Average 20 – 22 Above average 22 – 25 Excellent (natural limit) > 25 Likely enhanced (unnatural) ⚠️ Most natural athletes rarely exceed 25 FFMI without performance-enhancing substances.