I ordered a 9D for my size 8 child and it fits like an 8.5 or 9 wide...she has plenty of growing room in these shoes so its pretty appropriately sized.  Ive danced my entire childhood and I think a lot of people don't realize how tightly a ballet shoe should fit.  Its very soft leather that is meant to stretch to your foot. Toes should be at the edge so when you're moving: they're not shifting.  Its structured this way for stability.  It's not meant to fit like a sneaker.  Truthfully though toddlers don't need exact fit shoes because they're moves are clumsy: they're not doing pirouettes here...  So size up a size, and they can wear socks for a little bit. And that way you're not going to waste a ton of money on new shoes every few months.