I bought a little bigger than I needed for my granddaughter and it fit perfect.  It has a tie around the waist to cinch up any excess.  She is 2 1/2 years old and wears a size 2 or 3.  I read some other people saying if they wear a 2 or 3 to get a 3/4 and I did.  It looked too big when I pulled it out of the box but after I got it on her and tied the bow it was perfect and beautiful!  It comes below the knee and she is average height for her age maybe a little taller.  Shes not a stick but shes not overweight either.  Lovely material!  Well worth the money!