This might be dumb to ask, but how should a sneaker fit?
In the past, I usually get shoes where my toe is pretty much all the way to to the tip of the shoe.
I just bought a pair that were only available in one size. They are slightly bigger than my normal shoes. There is about a thumbs/fingers width between my heel and the back of the shoe if I push my toe all the way to the front. (about .5-.75" to the top when I stick my big toe up in the shoe).