I have to buy men's because I am a women's 11. I buy cycling shoes slightly larger, but not as large as running shoes. There's a fine line for me between shoes big enough to accommodate swelling and shoes so big they allow my foot to slide down in the shoe when i stand to pedal, causing my toes to hit the end and damage the toenail. I finally grew a toenail back from this happening in a 400k last year.