Calculator
FFMI calculator
Fat-free mass index — muscle mass scaled to height, so two people of different heights can be compared.
Work it out
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.
SOURCE·Kouri et al., fat-free mass index normalised to 1.8 m·REVIEWED JUL 2026