# 3/8 Inch BSP — Plumbing fitting and pipe thread standards

For 3/8 Inch BSP, thread standard is BSP; threads per inch (tpi) is 19; major (outside) diameter (mm) is 16.66, recorded from its source on 2026-08-12.

- **Thread standard:** BSP _(our reading, not quoted from the source)_
- **Nominal size:** 3/8 Inch BSP _(verified: appears in the quote below)_
- **Threads per inch (TPI):** 19 _(verified: appears in the quote below)_
- **Major (outside) diameter (mm):** 16.66 _(verified: appears in the quote below)_

## What the source says

> 3/8 Inch BSP | 16.66 mm | 15.2 mm | 19

## Source

- https://www.lsengineers.co.uk/advice-centre/bsp-thread-sizes-explained

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/).