Wide Sizes
Shoe size is a number representing the fit of a particular shoe on a person. Many shoe sizes are only for the length of a shoe because it is more expensive to manufacture shoes in many widths. However there are now a good number of brands that offer wide sizes. An example of a good brand with wide sizes for men and women is Clarks.
There is not a standard system for wide sizes because many major brands are not interested in the wide shoe market.
The system used by Clarks and other quality brands is: N (narrow), M (medium) or R (regular), W (wide), W (double wide). Wide and double wide are great wide sizes for people who need comfortable shoes.
Another common wide size system is: A, B, C, D, E, EE, EEE, EEEE, F, G. A is a very narrow shoe, E is a comfortable wide size for many people, EE through G are even wider to accommodate wide feet of all types.
One more less common size system is: 4A, 3A, 2A, A, B, C, D, E, 2E, 3E, 4E, 5E, 6E. 4A is the narrowest size and 6E is the widest.
The international standard for shoe size is called Mondopoint. It is detailed in ISO 9407:1991. A shoe size in this system is the average length of the foot / the average width in millimeters. An example size is 300/100, this means an average length of 300 millimeters and an average width of 100 millimeters. This system is not used anywhere in the world for civilian shoes, it is mainly used by NATO and other militaries.
A rule of thumb when buying wide shoes is to look for at least one W or E.