# 1-1/2 — Plumbing fitting and pipe thread standards

For 1-1/2, thread standard is NPT; threads per inch (tpi) is 11 1/2; thread pitch (mm) is 2.2087; major (outside) diameter (mm) is 48.2600; thread angle (degrees) is 60, recorded from its source on 2026-08-12.

- **Thread standard:** NPT _(our reading, not quoted from the source)_
- **Nominal size:** 1-1/2
- **Threads per inch (TPI):** 11 1/2
- **Thread pitch (mm):** 2.2087
- **Major (outside) diameter (mm):** 48.2600 _(verified: appears in the quote below)_
- **Thread angle (degrees):** 60 _(our reading, not quoted from the source)_
- **Governing standard:** ASME B1.20.1 _(our reading, not quoted from the source)_

## What the source says

> 1.900 | 48.2600 |

## Source

- https://en.wikipedia.org/wiki/National_pipe_thread

Last verified: 2026-08-12. Review by: 2028-08-11.
Part of [Plumbing fitting and pipe thread standards](https://referencesource.org/plumbing-fitting-thread-standards/).