Convert common drill bit sizes between fractional inch, decimal inch and millimeters.
Tools • drill sizes
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Drill bits come in fractional-inch, metric (mm), wire-number and letter sizes, and workshops mix all four. This chart converts the common drill sizes between fractional inch, decimal inch and millimeters.
It is essential for woodworking, metalworking and DIY when matching a bit to a hole, screw or tap — for example a 1/4" bit is 0.25" = 6.35 mm, with 6.5 mm being the nearest metric bit.