My 10 year old son is 5' tall and this robe (size Large) hits him just below the knees.  He is also quite thin which is a good thing because he can still pull the robe on over his head, but if he were heavy I think it would be too tight for him.

That being said, he really likes the robe and puts on his Harry Potter Quidditch goggles and just sits in that costume and reads books!  LOL.  Too funny!  It's nice for him to have a dress-up for imaginative play that's fun and not too babyish...  One last foray into childhood games!

Anyway, I like the robe, it's good quality, and it looks very sharp.