As you come out of your teens your growth should stop. There should of been little growth from when you were 16, maybe 2 or 3cm over the 2 years. 18 years onward should be no growth.
Greengrass is right it should level out in late teens, he may have a couple of cm of growth into his twenties but it wont be much. It's the other things that continue to grow like facial hair.
