R1/4 vs 1/8-27 NPT: specs compared
Updated 05 September 2026.
13.157 mm
R1/4 wins on major diameter
On major diameter, R1/4 leads: 13.157 mm versus 10.29 mm.
| Spec | R1/4 | 1/8-27 NPT |
|---|---|---|
| Designation | R1/4 | 1/8-27 NPT |
| Major diameter | 13.157 mm | 10.29 mm |
| Threads per inch / pitch | 19 | 27 |
| Thread form | tapered, 55 degree | tapered, 60 degree |
| Seals on | on the thread flanks with PTFE tape or paste | on the thread flanks with PTFE tape |
Questions and answers
Which has the higher major diameter, R1/4 or 1/8-27 NPT?
On major diameter, R1/4 leads: 13.157 mm versus 10.29 mm.
How do R1/4 and 1/8-27 NPT compare?
On major diameter, R1/4 leads: 13.157 mm versus 10.29 mm.