I ordered a large as they have girl 2-6x large is size 5-6.  They have a large for girls 7-16 and the large is 12-14.  I bought this for my 6 year old granddaughter.  Was surprised to see a 12-14.  HOWEVER, THERE ARE NO EXCHANGES OR RETURNS!  So, I'm SOL.

Be careful.  I didn't know Amazon had items that you couldn't at least exchange for the correct size.

It looks like a beautiful, BIG dress.