This is a size 5 in a boy's US Size. I would say that it would fit size XS Boys, if you are used to shopping with Letter sizing. My son wore this a handful of times but who doesn't love a great active wear deal! Especially for kiddos who seem to grow out of everything right when you purchase them! This sweatshirt has been well loved but shows no pealing of the NIKE logo on the chest. The therma-fit logo has a little fading but it is not rubbing off! Never placed in the dryer as all sweatshirts in my home get hung to dry. Tighter, straight fit and very durable in material. Let me know if you have any questions or need any measurements! No stains! Pet friendly home Non smoking home