NPT Size
1-1/4" NPT
Large process and plumbing connections where flow demands a bigger bore.
Last verified: 2026-07-10
| TPIThreads per inch (NPT is tapered at 3/4" per foot). | 11.5 |
|---|---|
| Pipe OD(in)Actual outside diameter of the thread / pipe. | 1.66 |
| Tap drillTypical tap drill for cutting the internal NPT thread. | 1-1/2" (1.500") |
| Typical use | Large process lines, plumbing headers |
Other npt pipe thread chart
Sources
- ANSI/ASME B1.20.1 — pipe threads, general purpose (NPT): TPI and pipe OD
- Typical NPT tap-drill charts (machining practice)