I read reviews that these ran too big, so I order the current shoe size my daughter is in right now. She wears a size 13 sneaker but can fit into ballet/sandals/slip on shoes size 12. These fit her perfectly in a size 13.  The strap on the back does adjust and the tongue area does as well, which right now it needs to be tightened to stay on her foot. I bought these to wear to Disney/sea world so if they get wet they will dry quicker and will stay on her feet for rides and running around. She says they are comfy and don't hurt, hope to re-review after some wear. My only negative which is NOT a deal breaker is you can see the glue that attached the rubber toe (photo)

Worked perfect for our open-close day at Disney for our 7 year old. She lasted the day and very few complaints of her feet hurting.