G1/8 vs 1/8-27 NPT: specs compared
Updated 05 September 2026.
10.29 mm
1/8-27 NPT wins on major diameter
On major diameter, 1/8-27 NPT leads: 10.29 mm versus 9.728 mm.
| Spec | G1/8 | 1/8-27 NPT |
|---|---|---|
| Designation | G1/8 | 1/8-27 NPT |
| Major diameter | 9.728 mm | 10.29 mm |
| Threads per inch / pitch | 28 | 27 |
| 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, G1/8 or 1/8-27 NPT?
On major diameter, 1/8-27 NPT leads: 10.29 mm versus 9.728 mm.
How do G1/8 and 1/8-27 NPT compare?
On major diameter, 1/8-27 NPT leads: 10.29 mm versus 9.728 mm.