It's been my experience that you have to be very careful with cycling shoes and sizing. I wear an 10 1/2 to 11 shoe, and can usually wear a 45 or 46. Currently, I have Shimano 45.5s. I'd go to your LBS and try on as many shoes of different brands as you can (Shimano, Specialized, Sidi, etc.) and make sure you determine what size works for you in each brand and go from there.