I ordered the 1-2 yr size because the other sizes 0-12 month  stopped fitting when my daughter was 3 months old!  The 1-2 year size fit her now and will fit her for a while younger, she is 4 months!  She is a bigger baby overall, so I took that into consideration in buying the bigger size (1-2yr) and i'm glad i did.  Other than the size issue, these socks are the cutest thing EVER. They really do look like little mary janes.  Too adorable.  Wish they would do half black/half brown though.  I love these socks so much, i had my mom pick up some tights just like them, which are also the most adorable thing ever!  LOVE THEM!! (expensive, so if you are money conscious buy bigger so you get more use!)