Got a medium for my grandson who is 7 yrs old and 62 lbs because I read that they were very stretchy and I didn't want them being saggy. They are very stretchy and he said they were comfortable because they are super soft, BUT they kept going in his butt and he didn't want to wear them because of that reason. Not sure if the larger size would be better or not. I had to very carefully use a thread ripper to get the tags off. No biggie though.