Calculator
FFMI calculator
Fat-free mass index — muscle mass scaled to height, so two people of different heights can be compared.
How it is calculated
FFMI divides lean mass by height squared, then normalises to a 1.8 m frame. It was proposed as a way of describing muscularity independently of height and fatness.
It is often quoted with a hard ceiling for drug-free lifters. That claim comes from a small study of a specific population and does not survive as a test of anybody's individual honesty — treat FFMI as a description, never as an accusation.