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This is great advice, and something I do myself.  It's important to note that no two brand's sizes run the same.  For that matter, even within a line things can run irregular.  Some of the reasons for this can be the cut, fabric, whether or not it has stretch, etc.  But it doesn't hurt to know which labels tend to fit you better than others.  It will help cut down shopping time and frustration when you are hitting the department stores and online shopping.