I bought these in a 39, which is what I wear in Dansko, and they were too small. I then bought them in a 40, and they were too big. My feet were absolutely swimming in the 40s. The 40s were also much wider than the 39s, but all I needed was more length. Now I don't know what to do, if I should try a 40 narrow, even though I've never worn a narrow in my life. My American shoe size is between an 8-8 1/2, though I definitely wear 8 1/2 for athletic shoes. But I have never worn a 9, and most of my regular shoes are an 8. So I think these shoes definitely run small. They are beautiful and much cheaper than Danskos. I also liked the arch a little bit more than Danskos. The Danskos arch is a little higher and harder. These felt more comfortable in the arch, but I guess I really need a 39.5. It is a huge difference going up a size.