i'm 5'7" 155lb. wear a size 8-10, pretty much always a Medium in dresses occasionally a large. I got a medium and I feel like it's a bit big on me. It fits pretty well in the shoulders but its big everywhere else. I know it's a shift dress but the medium fits more like a muumuu on me. I belted it and it's super cute but wish i had the option to wear it either way. I'm tempted to order another color in small and see if that works.