I wear a size 8. Period.  Based on the reviews of this prodcut I ordered an 8.5 and its still too small.  My heel is past the shoe edge.  I could order a 9, which I have never done in my 40+ years and it still doesnt seem it would fit.  The problem is the placment of the thong. It's too far back, so you have space at the toe area and the rest of your foot is left with very little room. Fail.