R4 vs 5-8 NPT: specs compared
Updated 05 September 2026.
141.3 mm
5-8 NPT wins on major diameter
On major diameter, 5-8 NPT leads: 141.3 mm versus 113.03 mm.
| Spec | R4 | 5-8 NPT |
|---|---|---|
| Designation | R4 | 5-8 NPT |
| Major diameter | 113.03 mm | 141.3 mm |
| Threads per inch / pitch | 11 | 8 |
| 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, R4 or 5-8 NPT?
On major diameter, 5-8 NPT leads: 141.3 mm versus 113.03 mm.
How do R4 and 5-8 NPT compare?
On major diameter, 5-8 NPT leads: 141.3 mm versus 113.03 mm.