They run small — I'm a 5.5 in Adidas, 5.5 to 6 in most Nikes, and these were snug at a 6. Nordstrom recommends ordering a size up; I'd recommend ordering a half-size up. They're so snug that after a while, they press down (and indent) the top of my feet.  https://theshoeinfo.com/best-shoes-for-dunking/