There have been numerous threads about this. I don't remember all the links. In general, the average guy is just about done in length by age 16, though often not completely. There is sometimes more growth in girth though in many guys after age 16.
However, there are guys who don't start puberty until about age 16.
It is not real common but guys dicks sometimes grow until age 25. There was a chart on a thread here that showed that the maximum length of an adult penis was actually when guys were in their early 30's. Only a tenth of an inch as I recall. It has to do with the strong sexual urge I suspect meaning more blood to the penis. But I don't know.
As for girls, I was taught and i taught what the heath books say about girls: girls grow faster than boys and the girls height is usually reached befroe age 16. Guys continue growing in height a foot after age 16, though not very common.