Drill Bit Size Converter
Convert any drill bit size between millimetres, decimal inches, inch fractions, number gauges and letter sizes: enter the size in mm and instantly see every equivalent, including the nearest gauge and letter match.
Result will appear here.
How to use
- Type the drill size in millimetres in the input box.
- The page updates live: see the size as decimal inches, the nearest 64th-inch fraction, and the nearest gauge number and letter size.
- Remember gauge and letter values are the nearest match — check the actual bit before drilling.
Note: In number gauges, a bigger number = smaller drill. Letter sizes run from A to Z.