I have vans 10.5 size boots. I have medium burton bindings that fit them really well. I also have rome XL bindings that are a good fit for my boots as well. I used to own a couple of pairs of ride bindings and they were a good fit with the 9-11 size bindings.
All boots have different external sizes relative to their size. Vans for example are generally quite bulky for each boot size, whereas some of the ride and 32 boots are a much thinner profile.
The only way to size correctly is to put boots in bindings and check the fit.