I normally wear 8.5 shoe, 9 athletic shoe. For Vionic I find that if they only come in full sizes, I always order size 8. Size 9 are always way too big. Important to get right fit so the arch support fits you correctly. I have an older pair of MaryJane style Vionic, the 8.5 was perfect. So when I ordered the 8.5 in this style was surprised it didn't work. The toe area is very narrow and really pinched my foot. Sent these back and took chances on the size 9. Lucked out and they are comfortable without sock. I think they are going to be a great shoe for summer. If interested in them I would suggest trying a half size larger then you normally wear