A standard full size ruler measures 12 inches in length. In addition to the marks for inches, many rulers also include a scale of 30 centimeters, allowing metric measurements.
In addition to the standard 12 inch ruler, rulers are also available in a number of commonly produced sizes. A yardstick has a length equivalent to three full size rulers, making it 36 inches long. A meter stick is slightly longer than a yard stick and is used to make metric measurements of up to 100 centimeters. Pocket rulers are generally six inches in length, and are often given away as advertising or promotional items.