3-8 NPT vs R3/4: specs compared
Updated 05 September 2026.
88.9 mm
3-8 NPT wins on major diameter
On major diameter, 3-8 NPT leads: 88.9 mm versus 26.441 mm.
| Spec | 3-8 NPT | R3/4 |
|---|---|---|
| Designation | 3-8 NPT | R3/4 |
| Major diameter | 88.9 mm | 26.441 mm |
| Threads per inch / pitch | 8 | 14 |
| Thread form | tapered, 60 degree | tapered, 55 degree |
| Seals on | on the thread flanks with PTFE tape | on the thread flanks with PTFE tape or paste |
Questions and answers
Which has the higher major diameter, 3-8 NPT or R3/4?
On major diameter, 3-8 NPT leads: 88.9 mm versus 26.441 mm.
How do 3-8 NPT and R3/4 compare?
On major diameter, 3-8 NPT leads: 88.9 mm versus 26.441 mm.