Pipe sizes confuse many first-time buyers. A "2 inch" pipe has an outside diameter of 60.33 mm, and "Schedule 40" has nothing to do with 40 mm. Here's how it works.
Nominal bore (NB / NPS)
The nominal size — ½", 1", 2", 4" and so on — is a name, not a measurement. For each nominal size the outside diameter stays fixed. That is why pipes of one size but different schedules all fit the same fittings.
Schedule = wall thickness
The schedule number sets the wall thickness. A higher schedule means a thicker wall, a smaller bore, more weight and a higher pressure rating. Stainless pipes use the "S" schedules from ASME B36.19: 5S, 10S, 40S and 80S.
- Sch 5S / 10S — thin wall, used for low-pressure process lines, water, food and pharma utilities.
- Sch 40S — the general-purpose standard for process piping.
- Sch 80S — heavy wall for high pressure, threading and corrosive service.
Quick reference
| NB | OD (mm) | 10S (mm) | 40S (mm) | 80S (mm) |
|---|---|---|---|---|
| ½" | 21.34 | 2.11 | 2.77 | 3.73 |
| 1" | 33.40 | 2.77 | 3.38 | 4.55 |
| 2" | 60.33 | 2.77 | 3.91 | 5.54 |
| 4" | 114.30 | 3.05 | 6.02 | 8.56 |
| 6" | 168.28 | 3.40 | 7.11 | 10.97 |
See the full table with weights per metre on our size charts page.
Seamless or welded?
Seamless pipes (ASTM A312 seamless) suit high pressure and temperature. Welded pipes are cheaper and fine for most utility and process lines. Larger diameters are usually welded.
Looking for SS pipes in Vadodara? See our stainless steel pipe range or request a quote.