I purchased the size 6 for my almost 6 year old. She's average height & 45 lb.s. She wears size 7 in Carters/Oshkosh clothes because those clothes typically shrink a bit after washing and drying... These underwear are snug on my daughter. I have washed and dried them at least 5 or 6 times at this point. They did shrink a bit. They lose a star for running small. All the other size 6 underwear we own fit well without being snug. I do like the quality of these. I'm probably going to buy a few more packs in size 8 & 10 because these offer a great deal of coverage in the crouch area, unlike most panties we've purchases in the the past.