Why seven

Well seven books is for several reasons, but I suppose the main one, I was seven years at my secondary school. That’s kind of standard in England. Seven is also a magical number. I wanted him to come of age at 17. It just seems a good number for a wizard to come of age. So that meant seven books, that meant seven years in his life. Also, it will take seven books to get Harry to the point where he has to face, um I can’t say. But in Book 7, you know, there’s a big climax coming here and it will take that many books to get him there.

— The Connection (WBUR Radio), 12 October, 1999 (Con: The Connection 1999)