24 inch pipe size
610 mm outside diameter
NPS 24 · DN600 · 24.016 in OD · 575.0 mm bore in schedule 40
What this pipe is for
The largest size in common schedule tables. NPS 24 is 24 inches across the outside, to within a fraction of a millimetre.
Here the number is the size
NPS 24 pipe is 24.016 inches across the outside — the NPS number exactly. From NPS 14 upward the designation finally becomes a measurement, which it is not at any smaller size.
The numbers
| NPS | 24 |
| DN (metric designation) | 600 |
| Outside diameter | 610 mm · 24.016 in |
| Wall, schedule 40 | 17.48 mm |
| Bore, schedule 40 | 575.0 mm · 22.639 in |
| Name against reality | the NPS number is the OD |
Outside diameter is the number that matters. It is fixed for a given NPS regardless of wall thickness, which is what lets a fitting made for schedule 10 thread onto schedule 80. The bore changes with the schedule; the outside never does.
Nearby sizes
| NPS | DN | OD | Sch 40 bore |
|---|---|---|---|
| 12 | 300 | 323.8 mm | 303.2 mm |
| 14 | 350 | 355.6 mm | 333.3 mm |
| 16 | 400 | 406.4 mm | 381.0 mm |
| 18 | 450 | 457.2 mm | 428.7 mm |
| 20 | 500 | 508 mm | 477.8 mm |
| 24 | 600 | 610 mm | 575.0 mm |
Frequently asked questions
What is the outside diameter of 24 inch pipe?
610 mm, or 24.016 inches. At this size the NPS number is the outside diameter, exactly.
What is the DN equivalent of NPS 24?
DN 600. DN is the metric designation and is just as nominal — DN 600 pipe is also 610 mm across, not 600. The two systems label the same pipe.
What is the inside diameter of 24 inch schedule 40 pipe?
About 575.0 mm (22.639 in), from an outside diameter of 610 mm and a 17.48 mm wall. Inside diameter changes with the schedule; outside diameter does not, which is why fittings are sized on it.
Why is NPS 24 not 24 inches?
It is. From NPS 14 upward the number is the outside diameter in inches — the scale becomes a measurement at exactly this point.