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Interactive / exact conversion

Drill Size Converter

Enter a metric, decimal-inch or fractional-inch diameter. The converter uses exact rational unit conversion and then compares the result with nominal number and letter sizes.

Examples: 6, 0.2010, 5/16, #7 or F.

Method

Decimal input is parsed as a rational number. Unit conversion uses exactly 25.4 mm per inch. Number and letter values use the versioned lookup array; fractional alternatives are rounded to the nearest 1/64 inch and clearly labeled as nearby, not exact.

Limitations

Nominal drill diameter does not guarantee finished-hole diameter. Runout, tool wear, point geometry, feed and work material all affect the result.