Standard NPT Tap Drill Sizes and Decimal Equivalents

Find the complete standard NPT tap drill sizes chart, including decimal equivalents for accurate conversions. Easily reference tap drill sizes from 1/16 to 3 inches for precise machining and threading applications.

Standard NPT Tap Drill Sizes and Decimal Equivalents
NPT Size Tap Drill Size (in.) Decimal Equivalent (in.)
1/16 – 27 C 0.242
1/8 – 27 Q 0.332
1/4 – 18 7/16 0.438
3/8 – 18 9/16 0.562
1/2 – 14 45/64 0.703
3/4 – 14 29/32 0.906
1 – 11 – 1/2 1-9/64 1.141
1 – 1/4 – 11 – 1/2 1-31/64 1.484
1 – 1/2 – 11 – 1/2 1-23/32 1.719
2 – 11 – 1/2 2-3/16 2.188
2 – 1/2 – 8 2-39/64 2.609
3 – 8 3-15/64 3.234

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