Bought an XS. I'm 5'3" and a size 0. XS fits perfectly, but it is fairly fitted. I would say if you can't wear a 0 then you want to go up to a small. Love how this ties to make it short or long. My thighs started to burn a little on our recent beach trip so I simply untied it to make a short dress. Very pleased overall with this. One word of caution is that white was not a smart choice for a beach trip. The sand really stained it and I wish I had gotten a darker color.