Depending on the BRAND and STYLE I'm either a 9.5 or 10. I have them in a 10 and my foot just fits the sole without sagging at all so they fit just right. I love these, they are so comfortable and easy to put on and take off. I'm not a fan of flip flops or sandals, but I hate wearing sneakers in the summer. This is the perfect hybrid/intermediate shoe type. Definitely a big fan!