Costume is very small. I have a small 5 year old who wears size 5 and the small was very tight on her. I looked at the measurements and measured my daughter, per the product measurements the costume should have been big on her (she was at the low end of the measurements). I sent this one back and ordered the medium (size 8-10) and it fit much better. I would definitely recommend ordering the next size up from your child's usual size.