Selecting the correct drill size for NPT threads is critical for getting a proper seal and avoiding rework. A well-organized NPT drill and tap chart makes it easy to find the right match, whether you need the 1/8 NPT tap drill size, the 1/4 NPT drill size, or the 3/8 NPT drill size. For larger fittings, references like the 1/2 NPT drill size or other pipe tap dimensions are just as important. This guide provides a clear reference chart to help machinists, fabricators, and engineers quickly identify the correct drill bit size for any NPT thread.
| NPT Size | Threads Per Inch | Drill Size | Decimal (inches) |
|---|---|---|---|
| 1/16″ NPT Tap | 27 | Letter R Drill Bit | 0.339 |
| 1/8″ NPT Tap | 27 | Letter Q Drill Bit | 0.332 |
| 1/4″ NPT Tap | 18 | 7/16″ Drill Bit | 0.438 |
| 3/8″ NPT Tap | 18 | 37/64″ Drill Bit | 0.578 |
| 1/2″ NPT Tap | 14 | 23/32″ Drill Bit | 0.719 |
| 3/4″ NPT Tap | 14 | 59/64″ Drill Bit | 0.922 |
| 1″ NPT Tap | 11.5 | 1-5/32″ Drill Bit | 1.156 |
| 1-1/4″ NPT Tap | 11.5 | 1-1/2″ Drill Bit | 1.500 |
| 1-1/2″ NPT Tap | 11.5 | 1-47/64″ Drill Bit | 1.734 |
| 2″ NPT Tap | 11.5 | 2-7/32″ Drill Bit | 2.219 |
| 2-1/2″ NPT Tap | 8 | 2-5/8″ Drill Bit | 2.625 |
| 3″ NPT Tap | 8 | 3-1/4″ Drill Bit | 3.250 |
| 4″ NPT Tap | 8 | 4-1/4″ Drill Bit | 4.250 |
See MISUMI USA’s full range of threading tools, including the following:
For questions on products related to NPT Drill and Tap sizes, or any other product questions please connect with our product experts and engineers. Also, be sure to check out our MechLab Blog, and find the answers to any questions you may have had (or not had) about NPT sizes like NPT thread fittings chart, and All about NPT thread fittings.
Disclaimer:
The content on this webpage is for informational purposes only. MISUMI makes no guarantees, expressed or implied, regarding the accuracy, completeness, or validity of the information. Performance parameters, tolerances, designs, materials, or processes should not be assumed to reflect third-party suppliers’ or manufacturers’ deliverables within MISUMI’s network. Buyers are responsible for specifying their part requirements.