G3/4 vs 3/8-18 NPT: specs compared
Updated 05 September 2026.
26.441 mm
G3/4 wins on major diameter
On major diameter, G3/4 leads: 26.441 mm versus 17.15 mm.
| Spec | G3/4 | 3/8-18 NPT |
|---|---|---|
| Designation | G3/4 | 3/8-18 NPT |
| Major diameter | 26.441 mm | 17.15 mm |
| Threads per inch / pitch | 14 | 18 |
| Thread form | parallel, 55 degree | tapered, 60 degree |
| Seals on | flat washer or bonded seal on the face | on the thread flanks with PTFE tape |
Questions and answers
Which has the higher major diameter, G3/4 or 3/8-18 NPT?
On major diameter, G3/4 leads: 26.441 mm versus 17.15 mm.
How do G3/4 and 3/8-18 NPT compare?
On major diameter, G3/4 leads: 26.441 mm versus 17.15 mm.