I pretty much always wear a 7.5 in regular shoes and sandals, but I had read a few reviews that said that these run a bit small, so I ordered both a 7.5 and an 8.  While the size 7.5 fit alright, my toes hung over the front end a bit.  The size 8 fit well and didn't have that problem, so I decided to stick with the 8's.  The adjustable strap in the back makes them nice and secure, and they fit really well.

Although the price on these seems high compared to comparable flat-sandal styles, these have a cushioned foot bed that make them much more comfortable than other sandals I have tried on.  I also bought the leopard ones, and they are absolutely adorable!  I know I'll get a lot of use out of these this summer since the pattern really goes with everything and is versatile.