When do late bloomers (boys) stop growing?

Growth centers close: You can only grow taller as long as your growth centers are open to new growth.The same hormones that signal puberty signal the growth centers to make a final push to new growth before closing. Late Bloomers just have a delay of growth beyond finishing at 16-17 (males) & may do so into their early 20's. An x-ray of the wrist/hand can be assessed for growth centers. If all closed, you are done.