Although there are over 40 wrench sizes available between 5/16 of an inch and 7 inches, some common sizes, in inches, are 5/16, 3/8, 7/16, 1/2, 9/16 and 5/8. The wrench size is not the same as the bolt size. For example, a bolt with a 5/16-inch diameter requires a half-inch wrench.
Wrenches are hand tools designed to perform a variety of tasks, such as loosening or fastening nuts and bolts. There also are a variety of wrench types and shapes, including fixed-sized and adjustable wrenches. Some different kinds of fixed-sized wrenches are open-ended, close-ended, combination and socket wrenches. The closed-ended wrench, also called a box wrench, may be suitable for either a hex or square nut.