FFMI of 18: what does it mean?

A normalized FFMI of 18 places a man in the "average" zone of the scale (17 to 20), slightly below the active male population average (around 19): ordinary muscularity, with no serious training or only a recent start. For a woman, the reading flips: 18 enters the "very good" zone (18 to 20), meaning well-developed muscle at fitness-athlete level. Visually, a man at 18 has a standard physique; a woman at 18 shows clear, athletic muscular development. For a man, the upper natural zones — above average from 20, very good from 22 — remain fully within reach with structured training, at roughly height² (m²) kg of fat-free mass per FFMI point.