I wear a 15 street shoe, and my tele boots are a 30.5. You shouldn't go with what people on here say. Instead, you should go to a shop and have one of the folks there do a proper boot fitting. They will help you find the proper size, will be able to address issues such as pronation, can create custom footbeds, can epxand the shell or the liner, etc. They'll also help match you up with a boot that meets both the needs of your skiing style and your foot shape.
Free your heel:
Free your mind