# 5/8 — Plumbing fitting and pipe thread standards

For 5/8, thread standard is BSPP; threads per inch (tpi) is 14; thread pitch (mm) is 1.814; major (outside) diameter (mm) is 22.911; minor diameter (mm) is 20.588, recorded from its source on 2026-08-12.

- **Thread standard:** BSPP _(our reading, not quoted from the source)_
- **Nominal size:** 5/8 _(verified: appears in the quote below)_
- **Threads per inch (TPI):** 14 _(verified: appears in the quote below)_
- **Thread pitch (mm):** 1.814 _(verified: appears in the quote below)_
- **Major (outside) diameter (mm):** 22.911 _(verified: appears in the quote below)_
- **Minor diameter (mm):** 20.588 _(verified: appears in the quote below)_
- **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

> BSPP G 5/8 | 5/8" | 14 | 1.814 | 22.911 | 21.749 | 20.588

## Source

- https://www.machiningdoctor.com/charts/bsp/

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/).