BMITool · Free health calculator
FFMI Calculator: Fat-Free Mass Index
Calculate Fat-Free Mass Index (FFMI) and normalized FFMI from your height, body weight, and body fat percentage to benchmark lean muscle mass independently of total body scale weight.
What FFMI measures
FFMI scales fat-free mass against height in meters squared, providing a metric of muscularity similar to how BMI measures overall body weight. Normalized FFMI adjusts for differences in stature above 1.8 meters.
FFMI vs standard BMI
Athletes and bodybuilders often register as overweight or obese on standard BMI charts due to high lean tissue. FFMI distinguishes lean muscle tissue from adipose tissue.
Natural reference benchmarks
In clinical and sports physiology studies, normalized FFMI scores between 18 and 22 represent typical natural athletic development, while scores above 25 rarely occur naturally without exceptional genetics.