im a size 8 and a 26 fits me perfectly....ive tried a 25.5 before and could rock them but I don't see the need to. 26 feels better, 25.5 is a smaller shell so my feet just feel cramped. I get no heel lift and barely have any room in the toe box, just enough to make things comfortable.
you should still always go to a boot fitter though. after 10 years (9 of those years having the same foot size) of ice hockey, rollerblading, snowboarding, and skiing I pretty much have my foot size dialed in. I know what fits. but boot size isn't just about length, things like width and arch play a role in getting the right size as well. so get yo shit fitted