Really depends. I'm a 10.5 in Barrie and just purchased some unlined Chukkas on the Leydon in 11D. Leydon is significantly narrower than Barrie. My foot is basically right in the middle of D and E width and fits in the Leydon D but just barely and that's on an unlined chukka so there's definitely some give there.
So I would say at it depends on a couple of things; namely how wide your foot is and what boot/shoe you are purchasing.