Drill Bit Sizes

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 bit size

chart contains tools up to 1.5 inches in diameter, but larger tools are also commonly used. Metric drill bit sizes define the diameter of the bit in terms of standard metric lengths.
In smaller sizes, bits are available in smaller diameter increments. This reflects both the smaller drilled hole diameter tolerance possible on smaller holes and the wishes of designers to have drill bit sizes available within at most 10% of an arbitrary hole size.
Metric drill bits are typically used for a variety of applications, including woodworking, metalworking, plastics, and masonry. Number drill bit gauge sizes range from size 80 (the smallest) to size 1 (the largest) followed by letter gauge size A (the smallest) to size Z (the largest).
Number and letter sizes are commonly used for twist drill bits rather than other drill forms, as the range encompasses the sizes for which twist drill bits are most often used. The fractional inch drill bit sizes start from 1/64 inch and scale up all the way to 1inch with 1/64inch increments.
Drill bits with fractional inch sizes are typically used for woodworking, metalworking, and general construction purposes. This drill bit size chart provides a list of sizes in several measurement systems, including fractional, metric, wire gauge number, and letter.