Determining shoe width is a fairly simple operation, though it can get tricky when there are different types of shoes involved, such as the difference between dress shoe width, hiking boot width and sport shoe width.
Measure your foot. You can use measuring tape or a ruler, or just use an old pair of the same type of shoe you want to purchase. For example, if a man has size 9 dress shoes and he wants another pair of size 9 dress shoes, the width is likely to be the same.
Determine the length of your foot. This is just a helpful thing to know when deciding what shoes you will buy. This can also help a little in determining your foot and shoe width. Write down your measurements for future reference (see Resources below).
Measure the width of the shoe. This is especially helpful if the shoe does not fit your foot correctly. Perhaps your measurements were incorrect or the shoes have different specifications when it comes to width. If the shoe doesn't fit, your measurements will most likely come out differently. If the shoe does fit in width, the length is probably the culprit.
Compile exact measurements. This can make a big difference when trying on different shoes. Use a ruler or millimetre tape measure. Get your measurements to the closest mark. Rounding to the nearest centimetre or inch can make a big difference.
Try on the shoes. Based on the width of your foot, try on a shoe size that fits your measurements. If they fit, the determination was correct. If not, the measurements may be off or the shoes may be made according to different length and width specifications.