Size purchased 7-8 years. My guy is 38 pounds and about 46 inches tall. There's room to save, but not so much that it's too big, there's room to grow! Looks great and FYI for mommy boys it has a zippered crotch so they can pee without taking the suit off =) My only issue is that the stitching and placement of my son's mask is a bit wobbly but I do Wouldn't buy it again and plan on getting my daughter and her two other younger brothers to wear the costume too so they can pretend together. Really great gift for a YouTube kid who loves Iron Man