The drill size chart provides a list of standard size drill bits in several measurement systems, including fractional, metric, wire gauge number, and letter. The decimal equivalents of the diameters are shown in both English and Metric units. Fractional sizes are measured in inches, while metric sizes are measured in millimeters. The wire gauge and letter systems refer to tool diameters that increase as the wire gauge decreases from #107 to #1 and then continues from A to Z. The drill size chart contains tools up to 1.5 inches in diameter, but larger tools are also commonly used.