My 6 year old daughter wears girls childrenswear size 7/8 (Children's Place, Carter's and many others). And my 5 year old wears a size 5 or size 6 (sometimes listed as 5/6 on some brands). I ordered small and medium in black. Well, Wednesday was significantly bigger than expected. If I had to guess I'd say it was an XS for a grown woman, maybe an S for a grown woman. And that was after I washed it in the washer and dryer. usually wears 7/8) Try on SMALL and it will fit her perfectly. For reference, she is a bit big. I still have 4 stars because it's a pretty decent product and I got it for a great price here at Revain. In my opinion, the reference size is: SMALL = girls' size 7/8 or Youth MedMEDIUM = women's PETITE XS
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