I order the 6 year size. The tag says 5-6 Y. My daughter wears 5T tops, but I buy xs in girls because I don't like her clothes being skin tight. The dress fits her really well, it doesn't stretch on her and is the tiniest bit baggy which is how I like it. The material is very stretchy, almost like a swimsuit material. The skirt part is a little longer than I thought. If you are wanting it to look fluffy like the picture, you will need a petticoat underneath. She is really happy with the dress, and can't wait to wear it for picture day.