There has to be a bunch of places for you to try them on near you. You have to remember that everyone has different width and volume feet. One size 12 foot can be very different from another size 12 foot, so you are going to get many different answers. If you are a true 11.5, like I am, the Muck boot in size 11 will probably feel pretty good except that your toes will jam into the front of the boot. With a 12, you can easily take up the extra space with another insole, which will actually make the boot more comfortable. In the end, boots are like bows, you really should try it first before buying.