Join Date: May 2008
Location: St. Albert, AB, Canada
All of our four cats, as well as every cat I've know from kitten to 3 years has had a growth spurt (filling out) just before 2 years.
Height-wise average cats will be done growing at about 9-10 months, but they'll usually be lanky and silly looking as they continue to slowly fill out. Then there's a final bit of filling out at 2.
Larger breeds, like Maine Coons, will finish filling out at 3-4. With some of that being appearance only, rather than weight or height, since their coat isn't fully 'in' until that age.