I usually wear a woman's 8 or occasionally an 8 1/2. I had to go to a 9 in the Mary Jane Crocs -- and they JUST fit. I really debated going up to the larger size (10!), but I'm glad I didn't. This past season, I could not get the regular Crocs (Beach or Caymans) to fit me. I was just too in between the sizes -- one was way too small and the other too big. I haven't had this problem before.