In shirts I typically wear 14-16, 1X and in bras I've been buying 42 B or C, depending on the bra.  I purchased this in the XL first and on the snuggest setting it fits a little less snug than I am normally comfortable, so I bought it in the Large and its a tad snug.  I think I'm just in between sizes... so I kept them both and I wear the looser one around the house, because I have to say its the most comfortable bra I have ever (EVER) put on.  Its stretchy, soft and wicks moisture away.  I wear the smaller one for better support when I go out of the house or to work.  The only thing I don't like is that it doesn't work well with low cut or V-neck shirts- it just rides a little too high on me for that, but for the most part, and for most of my wardrobe, these bras are the BOMB-diggity.  They do not give you uni-boob like some of the other sports bra options and they are not so tight that you can't breathe.  Its not going to be a great bra for a cocktail dress or anything like that, but if you want an excellent and comfy bra for the day to day grind...do yourself and your boobs a big favor and buy this now!!