I have difficult feet to fit. I generally wear between 8 1/2 to 9 in a medium to wide. It just depends. I always could go by the brand and know what size to buy, but that does not always hold true.
These shoes lacked support on the sides of the shoe. If the patent had been supported/not extremely flexible I might have kept them. They were very comfortable. They seemed to be a little wide but I felt that a medium might end up being a tad too tight. The heel is really, really low so instead of ordering in a different size and still not getting it right. I just ordered a completely different shoe which ended up costing more but I like better and is even more comfortable. Comfort is always my first factor in deciding on keeping a shoe.