Keep in mind that the listed 'last' of a boot (92, 97, 98, 100, 102mm etc) is in a 26 or size 8 boot, and there is no prescribed way of measuring it, so taking a tape measure across your foot is not gonna help you much. Instead of talking in mm I just think of parts of the boot as supper narrow, narrow, normal, wide and supper wide, then their is instep height, ankle shape, calf shape, ramp, toe box, arch more and more, all of which goes into getting a good fitting pair of boots. sum up: Let the pros do it.