What is a Drill Bit?

The term drill may refer to either a drilling machine or a drill bit used in the drilling machine. The drill size chart refers to the dimensions of the drill bit. Drill bits are the cutting tools of drilling machines. In order to create holes, drill bits are usually attached to a drill, which powers them to cut through the workpieces made of various materials. Drills come in different sizes, shapes, and materials, while the standard sizes of drill bits have been defined by organizations and described in the drill bit size chart.

Common Types of Drill Bit Sizes

  1. Metric drill bit sizes: the drill bit diameter is measured in the metric system. Metric drill sizes are primarily used in Europe. There are many standards used to define the drill dimensions, one of the most commonly used drill bit sizes is the British Standard BS 328 set including twist drill sizes between 0.2 mm and 25mm. BS 328 drill dimensions are defined as below.
ø0.2 to 0.98 mm N · 0.1 mm
N · 0.1 + 0.02 mm
N · 0.1 + 0.05 mm
N · 0.1 + 0.08 mm
N is an integer between 2 and 9
ø1.0 to 2.95 mm N · 0.1 mm
N · 0.1 + 0.05 mm
N is an integer between 10 and 29
ø3.0 to 13.9 mm N · 0.1 mm N is an integer between 30 and 139
ø14.0 to 25.0 mm M · 1 mm
M · 1 + 0.25 mm
M · 1 + 0.5 mm
M · 1 + 0.75 mm
M is an integer between 14 to 25
  1. Number and letter gauge drill bit sizes: the 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). Smaller sizes will be listed in the drill dimensions chart, but those are rarely encountered in practice. Number and letter gauge drill bit dimensions are often used for twist drill bits rather than other drill forms, and are still in common use in the U.S. and to a lesser extent in the UK. Number and letter gauges do not follow a formula or standard increments. They are loosely based on the Stubs Steel Wire Gauge.
  2. Fractional-inch drill bit sizes: the drill bit sizes are written as irreducible fractions. ANSI B94.11M-1979 specifies the size standard of straight shank twist drill bits with working length from 1/64 inch to 1 inch in increments of 1/64 inch.

Drill Size Chart/Table – Drill Bit Dimensions Chart

In this drill bit size table, standard size drill bits available in several measurement systems, you can find wire gauge number, letter, fractional and metric drill sizes. Fractional sizes are measured in inches and metric sizes are measured in millimeters. The wire gauge number ranging from 107 to 1 and letters ranging from A to Z.