Drill Size Conversion Chart: Inch to mm (Printable)

This drill size conversion chart covers all 64 fractional drill bits from 1/64 to 1 inch. Each row gives the decimal inch size, the exact size in millimetres and the nearest metric drill in 0.1 mm and 0.5 mm steps, with the difference so you can see whether the metric bit is slightly larger or smaller.

Free printable · PDF

2 pages
US Letter — choose “Fit to page” for A4
PDF, 6 KB

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Use it to find a standard bit in mm, to substitute a metric bit for an imperial one (1/8 in is 3.175 mm, so a 3.2 mm bit is the usual swap), or to place a metric size between two fractional bits — 12.5 mm falls between 31/64 and 1/2 in. Print the PDF for the workshop or use the Excel version to filter sizes.

Good for

Converting fractional drill bits to millimetres
Choosing a metric substitute for an imperial bit
A wall chart for a workshop or tool drawer

Tip: For tapping threads, use a tap drill chart instead: tap drills are chosen for thread engagement, not the nearest size.

7 files · PDF, DOCX

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