Let me say when I purchase a hat I have to do some serious research I have a very small head for an adult male. my head is 20'' 1/2 inches or a 6 3/4 in a fitted hat. I ordered the small and it was a little loose as I expected it to be, lucky this hat comes with Barmah hat sizers one for a full size and one for half a size I used both and now I have a nice snug fit with this hat. I did a a lot of research before buying this hat because let's be real 80-100 is a nice chunk for a hat. Believe the hype these hats are top quality, very nice in fit and finish I can't wait to purchase another! Do yourself a favor if you're on the fence get one you won't be disappointed.