Ordered the medium in gray for my skinny, taller-than-average 8 year old son, and it is just big enough to carry him into the next year or two without swallowing him whole.  This jacket is so lightweight that Im tempted to try an XL for myself!  Bonus points for the fact that the gray was at a MUCH lower price point than the other options.  Ill likely be back to purchase another one for my daughter when she grows out of her current coat.