Width: There is approximately a 1/2" difference between widths (2A, B, D, 2E and 4E) and a 3/8" difference between 4E and 6E width. This difference occurs across the ball of the foot and is the maximum difference in width. There is less of a width difference as you move toward the tip of the shoe and toward the heel.
Length: There is approximately a 1/6" difference between each half size (ie, between 9 and 9.5 and between a 9.5 and a 10, and so on). For every half size up, the width (across the ball) will increase by 1/8".
We cannot provide exact measurements for every style we produce, but we hope this general information is helpful.