Bought an xl. I’m 5’10”, not a stick, not fat, athletic body. 175lbs.... this fit great. Long enough from crotch to waist, really soft material. Super cute. Will order more. I would imagine a large would fit someone 5’7” 150 lbs, medium would be someone you’d consider petite- maybe 5”5 130lbs and a small could fit an 11 year old lol ... my point- go a size up.