I ordered 7-8 and they were smaller than expected. They were for a skinny 9 year old who normally wears size 8 pants. Size 7-8 is similar to size S/6 or maybe smaller. I would go up a size or maybe even 2 sizes if I order another. She could at least still wear them during the day and they were very cute. She also has long legs and there was no problem with the length.