1/4
For 1/4, thread standard is NPT; threads per inch (tpi) is 18; thread pitch (mm) is 1.4111; major (outside) diameter (mm) is 13.716; thread angle (degrees) is 60, recorded from its source on 2026-08-12.
- Thread standard
- NPT our reading
- Nominal size
- 1/4
- Threads per inch (TPI)
- 18
- Thread pitch (mm)
- 1.4111
- Major (outside) diameter (mm)
- 13.716 verified
- Thread angle (degrees)
- 60 our reading
- Governing standard
- ASME B1.20.1 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
0.540 | 13.716 |
— en.wikipedia.org, 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.
Thread pitch (mm)
en.wikipedia.org says thread pitch (mm) is 1.4111, as of 2026-08-12.
0.540 | 13.716 |
https://en.wikipedia.org/wiki/National_pipe_thread
geminivalve.com says thread pitch (mm) is 1.41122, as of 2026-08-12.
1/4 | 18 | 0.05556 | 1.41122 | 0.54 | 13.72
https://www.geminivalve.com/bsp-thread-vs-npt-fitting/
Major (outside) diameter (mm)
en.wikipedia.org says major (outside) diameter (mm) is 13.716, as of 2026-08-12.
0.540 | 13.716 |
https://en.wikipedia.org/wiki/National_pipe_thread
geminivalve.com says major (outside) diameter (mm) is 13.72, as of 2026-08-12.
1/4 | 18 | 0.05556 | 1.41122 | 0.54 | 13.72
https://www.geminivalve.com/bsp-thread-vs-npt-fitting/
trimantec.com says major (outside) diameter (mm) is 13.7, as of 2026-08-12.
-04 (1/4) | 18 | 13.7 | 0.54 | 12.4 | 0.49
Sources
- en.wikipedia.orghttps://en.wikipedia.org/wiki/National_pipe_thread
- geminivalve.comhttps://www.geminivalve.com/bsp-thread-vs-npt-fitting/
- trimantec.comhttps://trimantec.com/blogs/t/thread-identification-guide