Mephisto shoes claim to be the "finest walking shoes" and I wholeheartedly agree. (I practly live in "helen" and "violette" model sandals.)
Below is a Mephisto shoe sizing chart that I've found to be very accurate for their shoes.
If you're like me, you have a closet full of a range of shoe sizes and determining a European shoe size can be more than a little difficult.
Let me use my own foot as an example. The most important factor in determining size is the length from heel to toe. In my case, it's exactly 10 inches. In most womens sandals I wear a U.S. size 8.5 and a European size 39. For flat dress shoes, a ladies U.S. 9 or European 40 will do. For sports shoes where heavy socks are required, I prefer a ladies U.S. 10 (especially in Japanese-made brands) or European 41. For heeled dress shoes, a ladies U.S. size 9.5 will do but, for a 10" foot, I wouldn't recommend more than a European size 40.
From my experience with Mephisto shoes, their European sizes run just a little to the short side when comparing with U.S. sizes. For example, Mephisto lists a European 39 as a U.S. 8.5 or 9. It's in between but, much closer to a 8.5. As I've mentioned, for me, this is perfect for sandals but, a little short for dress shoes.
You'll be lucky to win an auction for a pair of NEW Mephisto sandals for less than $75. I've paid $100 for a new pair myself and considered it a deal since retail is about $135 for the new "hadassa" sandals.
Be wary of USED Mephisto sandals with a cork footbed. The cork footbeds quickly mold to the shape and size of the wearer. If too old, you'll miss out on all of their wonderful support. Personally, I buy a new cork pair after 6-12 months of daily wear.
I hope you've found this guide helpful. Happy walking!
Men & Women - EU to U.S. Shoe Size Chart