Cycling shoes have stiff soles to transfer as much power to the pedals as possible. You buy a half size larger in American sizing, one size larger in Euro sizing, to accommodate swelling of your feet. Different cycling shoe companies measure a little different from one another.

Take me for example: I wear a US 9 1/2 for my sneakers, dress shoes, and work boots with ease. My Specialized MTB shoes are 44 and my Shimano road bike shoes are 45. I always try shoes on before buying them, and never catalog or internet order shoes.

For my cycling shoes, I always wear a thin sock, usually a cycling specific sock. The snug fit helps prevent blisters.