16 inch pipe size
406.4 mm outside diameter
NPS 16 · DN400 · 16.000 in OD · 381.0 mm bore in schedule 40
What this pipe is for
Large process and transmission piping, with the NPS number equal to the outside diameter in inches.
Here the number is the size
NPS 16 pipe is 16.000 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 | 16 |
| DN (metric designation) | 400 |
| Outside diameter | 406.4 mm · 16.000 in |
| Wall, schedule 40 | 12.7 mm |
| Bore, schedule 40 | 381.0 mm · 15.000 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 |
|---|---|---|---|
| 8 | 200 | 219.1 mm | 202.7 mm |
| 10 | 250 | 273 mm | 254.5 mm |
| 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 16 inch pipe?
406.4 mm, or 16.000 inches. At this size the NPS number is the outside diameter, exactly.
What is the DN equivalent of NPS 16?
DN 400. DN is the metric designation and is just as nominal — DN 400 pipe is also 406.4 mm across, not 400. The two systems label the same pipe.
What is the inside diameter of 16 inch schedule 40 pipe?
About 381.0 mm (15.000 in), from an outside diameter of 406.4 mm and a 12.7 mm wall. Inside diameter changes with the schedule; outside diameter does not, which is why fittings are sized on it.
Why is NPS 16 not 16 inches?
It is. From NPS 14 upward the number is the outside diameter in inches — the scale becomes a measurement at exactly this point.