I wear an 8.5 regularly. I ordered both and 8 and a 9. The 8's were way too small and the 9's were a better fit so I kept them. I did a lot of research about these before I bought them and I liked that they were used by lifeguards without being slippery when wet. Unfortunately, I found them to be very slippery when the foot bed got wet. The sole was not slippery and did not lose traction bit my foot was sliding all over making them unsafe for me to where around pool. That said, I have worn them all day without the usual aching other flip flops have given me due to plantar fasciitis. The arch support is good, just wish the heal cup was a bit deeper as my heal drifts. I do like these and am able to wear them a long time but I prefer the support of Spenco over these for more vigorous use.