We recently bought my son new sneakers for everyday wear; the foot rug at the store said he needs a size 10, which we bought, and they fit him securely but had room to grow.  Since I want to use these boots awhile, I ordered an 11/12, knowing they would probably be roomy now but give him some time to wear them out before he outgrows them, and that's what I got.  With good thick socks, they're ideal for the snow we currently have and will be great rain boots for him this spring and hopefully summer.  Sufficient tread on the bottom and my son loves that he can put them on and take them off himself.