1/2
For 1/2, thread standard is BSP; threads per inch (tpi) is 14; thread pitch (mm) is 1.814; major (outside) diameter (mm) is 20.955; minor diameter (mm) is 18.631, recorded from its source on 2026-08-12.
- Thread standard
- BSP our reading
- Nominal size
- 1/2 verified
- Threads per inch (TPI)
- 14 verified
- Thread pitch (mm)
- 1.814 verified
- Major (outside) diameter (mm)
- 20.955 verified
- Minor diameter (mm)
- 18.631 verified
- Thread angle (degrees)
- 55 our reading
- Governing standard
- ISO 228-1 our reading
Values marked our reading are our classification of what the source says — the source does not print them in those words. The quote below is the evidence for each one; judge it yourself.
What the source says
1/2 | 14 | 1.814 | 1.162 | 20.955 | 19.793 | 18.631 |
— amesweb.info, retrieved 2026-08-12
Sources disagree
More than one authority states this, and they do not state the same thing. Both are reproduced with the source each came from — deciding between them is yours, not ours.
Major (outside) diameter (mm)
amesweb.info says major (outside) diameter (mm) is 20.955, as of 2026-08-12.
1/2 | 14 | 1.814 | 1.162 | 20.955 | 19.793 | 18.631 |
https://amesweb.info/Screws/BSP-Thread-Chart.aspx
geminivalve.com says major (outside) diameter (mm) is 20.955, as of 2026-08-12.
1/2 | 14 | 0.0714 | 1.814 | 0.825 | 20.955 | 0.7336 | 18.633 | 0.3214 | 8.164
https://www.geminivalve.com/bsp-thread-vs-npt-fitting/
htsspares.com says major (outside) diameter (mm) is 20.99, as of 2026-08-12.
1/2 Inch BSP | 20.99 mm / 3/4" | 14
https://www.htsspares.com/blog/how-to/how-to-measure-your-bsp-fittings
trimantec.com says major (outside) diameter (mm) is 20.8, as of 2026-08-12.
-08 (1/2) | 14 | 20.8 | 0.82 | 19.1 | 0.75
https://trimantec.com/blogs/t/thread-identification-guide
Minor diameter (mm)
amesweb.info says minor diameter (mm) is 18.631, as of 2026-08-12.
1/2 | 14 | 1.814 | 1.162 | 20.955 | 19.793 | 18.631 |
https://amesweb.info/Screws/BSP-Thread-Chart.aspx
geminivalve.com says minor diameter (mm) is 18.633, as of 2026-08-12.
1/2 | 14 | 0.0714 | 1.814 | 0.825 | 20.955 | 0.7336 | 18.633 | 0.3214 | 8.164
Sources
- amesweb.infohttps://amesweb.info/Screws/BSP-Thread-Chart.aspx
- geminivalve.comhttps://www.geminivalve.com/bsp-thread-vs-npt-fitting/
- htsspares.comhttps://www.htsspares.com/blog/how-to/how-to-measure-your-bsp-fittings
- trimantec.comhttps://trimantec.com/blogs/t/thread-identification-guide