G1/2 vs 1/4-18 NPT: specs compared
Updated 05 September 2026.
20.955 mm
G1/2 wins on major diameter
On major diameter, G1/2 leads: 20.955 mm versus 13.72 mm.
| Spec | G1/2 | 1/4-18 NPT |
|---|---|---|
| Designation | G1/2 | 1/4-18 NPT |
| Major diameter | 20.955 mm | 13.72 mm |
| Threads per inch / pitch | 14 | 18 |
| Thread form | parallel, 55 degree | tapered, 60 degree |
| Seals on | flat washer | on the thread flanks with PTFE tape |
Questions and answers
Which has the higher major diameter, G1/2 or 1/4-18 NPT?
On major diameter, G1/2 leads: 20.955 mm versus 13.72 mm.
How do G1/2 and 1/4-18 NPT compare?
On major diameter, G1/2 leads: 20.955 mm versus 13.72 mm.