I got an XS for my 5 year old who wears an XS or 5/5T. It's more like a 4T. I could barely tell the difference between the 3T I got. I got the same brand t-shirt in an XS and it will fit just fine. Unfortunately I didn't have time to exchange it for the right size, so he got a sweatshirt that's too small. I got this sweatshirt in 3T, kids xs, adult S-XL. Every other size was accurate for a unisex sweatshirt. They are very warm and soft on the inside. I would order them again, just order up on the kids size.