A medium fits me at 125lbs 5'5" loosely and comfortably. They are very soft and cozy. They are warm/hot and not for summer but perfect for winter. The fabric is not too thick (i think it just doesn't breathe). One last weird thing to mention, I have sensitive skin so I kind of despise seams in clothing (going so far as to sleep with my PJ's inside-out so the seams don't rub my skin) and these pants have moderately annoying seams for me (likely not noticeable by normal people)