So size up no matter what the size chart says. I followed the sizing chart and measured some of my son's existing clothing and ordered. The shirt that arrived was two sizes too small and was several inches different than the sizing chart. I emailed and rush ordered a new shirt for our Disney Trip. I did have to pay return shipping which is a little annoying since the size chart being several inches off is not my problem. Shirt is adorable but really order 2-3 sizes up.