NPT Size
1/8" NPT
The smallest common NPT size — instrumentation, gauges, and small pneumatic/hydraulic ports.
Last verified: 2026-07-10
| TPIThreads per inch (NPT is tapered at 3/4" per foot). | 27 |
|---|---|
| Pipe OD(in)Actual outside diameter of the thread / pipe. | 0.405 |
| Tap drillTypical tap drill for cutting the internal NPT thread. | R (0.339") |
| Typical use | Gauge ports, instrumentation, small air/fluid fittings |
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)