Originally Posted by MoveAlong
There is no average length/girth for anybody under 18 because puberty varies so much.
I second this comment.
Puberty hits all of us differently due to DNA/Genes. We discover traits that make us who we really are on the inside as well as out. Some sprout faster, some are slow bloomers. Most adolescents acheived the final stage of puberty around 18-21, I believe.