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Steel Pipe Sizes Chart
Nominal bore, outside diameter and common schedules for steel pipe.
| NB | OD (mm) | Sch 40 wall (mm) |
|---|---|---|
| ½” | 21.3 | 2.77 |
| 1″ | 33.4 | 3.38 |
| 2″ | 60.3 | 3.91 |
| 3″ | 88.9 | 5.49 |
| 4″ | 114.3 | 6.02 |
| 6″ | 168.3 | 7.11 |
Nominal bore (NB) is a size label — the OD is fixed and the schedule sets the wall thickness (Sch 40, 80, etc.). We supply steel pipe (ERW & seamless) and hollow sections.
Frequently asked questions
What is the difference between NB and OD?
NB (nominal bore) is a size label; OD (outside diameter) is the actual measured outer diameter, which stays fixed as the schedule (wall) changes.
What does Schedule 40 mean?
A standard wall-thickness class — higher schedule numbers mean thicker walls for the same OD.
ERW or seamless pipe?
ERW is economical for general/structural use; seamless suits higher-pressure applications.
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