As another review was so kind to explain for the rest of us, I normally wear a US Women's 9 shoe, but being that I opted for the PU version of the black flat, I sized down to the 8.5. On the first try-on, they were a little snug around the toes, but after a few short hours, they have stretched out nicely and are perfectly comfortable to walk around the office all day in! Great deal on a cute and simple flat!