shoe size

   All shoe sizes express in some way the approximate length of the shoe, or at least the length of the last, the form on which the shoe is made. In the U.S., a difference of one full shoe size represents a length difference of 1/3 inch (8.47 mm), so shoe size n represents a length of Z + n/3, where Z is the length of a size 0 shoe (if there were such a thing). The value of Z is 3-11/12 inches (99.5 mm) for infants' and boys' shoes, 3-7/12 inches (91.0 mm) for girls' shoes, 7-11/12 inches (201.1 mm) for women's shoes, and 8-1/4 inches (209.6 mm) for men's shoes. The size number for a woman's shoe is 1 larger than for a man's shoe of the same length (for example, a man's 7-1/2 is the same length as a woman's 8-1/2). In Europe, shoe sizes are measured in Paris points, a unit equal to 2/3 centimeter. Ski boots and hiking boots worldwide are measured in mondo points, which are simply millimeters. Link: Wikipedia has information on other shoe size systems used in Britain, Japan, and Australia.