SAE stands for "Society of Automotive Engineers." Established in 1905 at the dawn of the automotive industry, the SAE is still active today and boasts well over 100,000 members. One of its accomplishments was the establishment of standards of measure for a wide range of tools and materials having to do with the American auto industry. Today, only a few countries still make use of the SAE measurement system for tools. The metric system has been adopted everywhere else.
SAE tools and fasteners are designated by fractions of an inch, such as a 1/2-, 5/8- or 15/16-inch wrench or nut. In comparison, metric tools and fasteners are measured in millimeters, such as an 18 mm or 20 mm socket or bolt.
