Want Your Own Copy? American National Standards Institute (ANSI) drill bit sizes are used predominantly in the United States and utilize the Imperial measurement system. Drill bit sizes under ANSI are given in fractions of an inch, typically starting at 1/64 inch, then incrementing in 1/64 inch steps for smaller sizes, and up to larger sizes such as 1/2 inch, 1 inch, and so on. The system also includes a number series (from size 80, the smallest, to size 1) and a letter series (from A to Z), both used for diameters smaller than 1/4 inch. This provides a broad
