Every child is an individual and they all come in different shapes and sizes. Most items fit true to size, but European and Asian sizes are often smaller than Canadian and USA sizes. If you're unsure, always size up! If it arrives too big, they may not be able to fit the item this season, but they can always wear it next season. They will never be able to wear an item that is too small. My daughter is an average 4 year old who wears a size 5-6 in Canadian clothes. My son is tall but slim, so often wears smaller sizes. You know your child best, choose sizes accordingly and if there is a measurement chart available for the item, please use it.