Best thing to do is a shell size at a shop to know for sure. I am in a 25.5, but in other company boots I wear a 26. The 25.5 is really a 25 in the full tilt. With the moldable liner you get more room in the boot than with a traditional liner allowing me to be in 2 sizes smaller than my street shoe. Whats your street shoe size? Standard rule of thumb in ski boot sizing, one size smaller than your street shoe. If you use a foot bed that will take up some room as well. I don't use custom ones, thin old raichle stock liner foot beds.