I would be a L (5'6'', 178 lbs) but I did over one size larger, the XL, because I like mine roomy and relaxed, and also just in case the rayon shrinks, which Rayon usually does, but not much at all in this case, thank goodness. I wish there are hidden pockets, which make this dress perfect ... but otherwise a great easy piece to wear around the house or go out.