What size am I???

Hate to complain but what is with sizes at stores??? I am any where from a 2 to an 8 or in Juniors a 3 to a 9.  I thought the concept behind sizes was that you would go anywhere and know it. Not so. Oh well! It was great to have a size 4 be too big at New York & Co. (Although I didn't even try on the 2 because what if it was too small??? hahaha)