# 1 ½ — Plumbing fitting and pipe thread standards

For 1 ½, thread standard is BSP; threads per inch (tpi) is 11; major (outside) diameter (mm) is 47.8, recorded from its source on 2026-08-12.

- **Thread standard:** BSP _(our reading, not quoted from the source)_
- **Nominal size:** 1 ½ _(verified: appears in the quote below)_
- **Threads per inch (TPI):** 11 _(verified: appears in the quote below)_
- **Major (outside) diameter (mm):** 47.8 _(verified: appears in the quote below)_

## What the source says

> -24 (1 ½) | 11 | 47.8 | 1.88 | 45.5 | 1.79

## Source

- https://trimantec.com/blogs/t/thread-identification-guide

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/).