# 1-1/8 — Plumbing fitting and pipe thread standards

For 1-1/8, thread standard is BSP; threads per inch (tpi) is 11; thread pitch (mm) is 2.309; major (outside) diameter (mm) is 37.897; minor diameter (mm) is 34.939, recorded from its source on 2026-08-12.

- **Thread standard:** BSP _(our reading, not quoted from the source)_
- **Nominal size:** 1-1/8
- **Threads per inch (TPI):** 11
- **Thread pitch (mm):** 2.309
- **Major (outside) diameter (mm):** 37.897 _(verified: appears in the quote below)_
- **Minor diameter (mm):** 34.939
- **Thread angle (degrees):** 55 _(our reading, not quoted from the source)_
- **Governing standard:** ISO 228-1 _(our reading, not quoted from the source)_

## What the source says

> 1.4920 | 37.897

## Source

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

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/).