A shoe width chart can be adjusted by adding or subtracting increments of one-sixteenth to one-eighth of an inch for each adjustment from narrow to extra-wide. Determining, measuring and adjusting shoe width is a complicated issue in the shoe industry since widths are not a predetermined universal measurement and vary depending on the manufacturer and gender sizing.
Because the footwear industry does not maintain standard measurements for shoe width, those who fit shoes as a profession support the existence of multiple sizes. Each shoe manufacturer creates a unique form of measuring the width and labelling the shoe according to the designer's guidelines. Shoe designers do not consult other designers nor use a formula for shoe width. They estimate how wide a shoe should be and label it from AA, the narrowest, to EE, the widest.
Most European sizes do not come in widths and are produced only in a medium width. The only accurate way to determine proper shoe width size is to try the shoe on as most shoe width charts are derived from averages and approximations. A shoe that is the correct size and width will align the edges and bottom of the foot perfectly with the shoe's footbed.