NPT Size
3/8" NPT
Mid-size port between 1/4" and 1/2" — common on pumps, manifolds, and fittings.
Last verified: 2026-07-10
| TPIThreads per inch (NPT is tapered at 3/4" per foot). | 18 |
|---|---|
| Pipe OD(in)Actual outside diameter of the thread / pipe. | 0.675 |
| Tap drillTypical tap drill for cutting the internal NPT thread. | 37/64" (0.578") |
| Typical use | Pumps, manifolds, medium-flow 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)