I'm an 8.5/9 women and went with 40 and it fits well. If you're closer to an 8/8.5, or have a more narrow foot, 39 would work. They run slightly smaller than a traditional euro sizes (40 is usually too big for me). Euro sizes are 8-8.5= 39, 9-9.5=40, so if you're split on the half to larger size like I am, Euro sizing doesn't fit that great.
Answered on 5/10/2016 1:18:41 AM by Namase from Washington DC
Wow---update! Realized I got a 41 for my 8.5/9 feet! So it's not actual standard euro sizing. The rest of what I said rains true for euro shoes, but with these you should get a 40 for 8.5 women if they're on the narrow side or split between 8/8.5. I'm 8.5/9 and went with 41 and they fit perfectly. So they run a full size smaller than standard euro. Sorry for the mix up on my first answer!
Answered on 5/10/2016 1:22:33 AM by Namase from Washington DC