NPT Tap Drill Chart
Use this National Pipe Taper (NPT) tap drill chart to match a pipe tap with its recommended drill bit size. Each linked tap and drill bit leads directly to the corresponding product, and available matching tap-and-drill kits are linked in the third column. Browse our full selection of NPT pipe taps or shop NPT tap and drill sets for convenient matching combinations.
NPT threads are tapered and commonly used for threaded pipe connections. Pipe tap sizes are nominal pipe sizes, not the actual outside diameter of the tap or the drilled hole. Confirm the appropriate drill size, thread engagement, and sealing requirements for your material and application before machining.
NPT Tap and Drill Size Chart
| NPT Tap Size | Recommended Drill Size | Matching Tap and Drill Set |
|---|---|---|
| 1/16" NPT Tap | "D" Drill Bit | 1/16" NPT Tap and Drill Set |
| 1/8" NPT Tap | "R" Drill Bit | 1/8" NPT Tap and Drill Set |
| 1/4" NPT Tap | 7/16" Drill Bit | 1/4" NPT Tap and Drill Set |
| 3/8" NPT Tap | 37/64" Drill Bit | 3/8" NPT Tap and Drill Set |
| 1/2" NPT Tap | 23/32" Drill Bit | 1/2" NPT Tap and Drill Set |
| 3/4" NPT Tap | 59/64" Drill Bit | 3/4" NPT Tap and Drill Set |
| 1" NPT Tap | 1-5/32" Drill Bit | 1" NPT Tap and Drill Set |
| 1-1/4" NPT Tap | 1-1/2" Drill Bit | Sold individually |
| 1-1/2" NPT Tap | 1-47/64" Drill Bit | Sold individually |
| 2" NPT Tap | 2-7/32" Drill Bit | Sold individually |
| 2-1/2" NPT Tap | 2-5/8" Drill Bit | Sold individually |
| 3" NPT Tap | 3-1/4" Drill Bit | Sold individually |
| 3-1/2" NPT Tap | 3-3/4" Drill Bit | Sold individually |
| 4" NPT Tap | 4-1/4" Drill Bit | Sold individually |
Note: Sizes and product links follow the original reference chart. For 3-1/2" and 4" NPT taps, the listed drill sizes are not linked to individual drill products.
How to Use This NPT Chart
- Find the nominal NPT tap size required for your fitting or pipe connection.
- Use the recommended drill size in the second column to prepare the hole.
- Select the linked tap and drill bit individually, or choose the matching kit when available.
- Verify tap depth and thread fit with the applicable specifications and gauges; tapered pipe threads require attention to engagement depth.
Popular NPT Pipe Tap Sets
Need several NPT tap sizes? These sets group commonly used pipe taps together:
- 5 Piece Carbon Steel NPT Pipe Tap Set — 1/8", 1/4", 3/8", 1/2" and 3/4"
- 6 Piece Carbon Steel NPT Pipe Tap Set — 1/8", 1/4", 3/8", 1/2", 3/4" and 1"
- 3 Piece Carbon Steel NPT Pipe Tap Set — 1", 1-1/4" and 1-1/2"
- 6 Piece Carbon Steel NPT Pipe Tap Set — 1/4", 3/8", 1/2", 3/4", 1" and 1-1/4"
NPT Tap Drill Size FAQs
What does NPT mean?
NPT stands for National Pipe Taper. Its tapered thread form is used for threaded pipe connections, where thread engagement and the appropriate sealing method matter.
Is the NPT tap size the same as the drill diameter?
No. NPT tap sizes are nominal pipe sizes. The required drilled hole is a different diameter; use the drill-size column for the matching recommendation.
Can I buy the NPT tap and drill bit together?
Yes, several sizes in the chart link to matching tap and drill sets. Larger sizes are marked as sold individually when no matching set is listed.
Do NPT threads require sealant?
Many NPT applications use a compatible thread sealant or tape, depending on the fitting, fluid, pressure, and manufacturer instructions. The thread form alone does not guarantee a leak-free joint.
Are NPT and NPSC taps interchangeable?
No. NPT is tapered, while NPSC is a straight pipe-thread form. Check the specified thread standard before choosing a tap or drill size.
For additional references, see our tap and drill sizes chart and tap drill chart.