My daughter wears a 7/8 but being that it runs a little small in my opinion, I ordered her the large. I purchased this same jacket when she was 3 and ordered a size bigger and she had it for 2 years. So I knew to order her a large instead of medium. It fit just right, sleeves a little long but I can roll them. Shell have it for about 2 years again, Im glad I ordered on amazon in the store this jacket is $25.99 or more.