Drill Bit Size Converter

Convert drill bits between fractional inches, decimal inches and millimeters.

Size (fraction like 3/8, or decimal):

–Decimal (in)

–Millimeters

–Nearest 1/64″

How to use

Enter a fraction like 3/8 or a decimal — mm and nearest standard sizes appear; everything runs in your browser.

What is a 1/4-inch bit in mm?

6.35 mm — the chart covers 1/16″ to 1″ in 1/64″ steps.

What about number/letter gauges?

Numbered bits (#1–#80) run 0.228″ down to 0.0135″; this tool covers fractional sizes.

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