How to interpret FFMI
Use a body-fat estimate and height to index lean mass.
Measure body fat
Use the same method each time; scales, calipers and scans can differ by several points.
Enter height and weight
Use current values and the unit shown in each label.
Read the band
Treat the band as a rough comparison, not a medical assessment.
What does this tool do?
FFMI divides fat-free mass by height squared, giving a height-adjusted picture of lean tissue. Normalising to a height of 1.8 m makes comparisons between people of different heights more reasonable.
The Formula
FFM = weight × (1 − body fat % ÷ 100); FFMI = FFM ÷ height²; normalised FFMI = FFMI + 6.1 × (1.8 − height in m)Frequently Asked Questions
What does a high FFMI mean?
It suggests a large amount of lean mass for height. Values above about 25 in men are rare and often reflect a body-fat measurement error rather than drug-free muscle.
Why report a normalised FFMI?
FFMI tends to rise with height even at the same muscularity. Normalising to 1.8 m makes comparisons between people of different heights fairer.