Pipe Size Converter
Convert nominal pipe size (NPS) to outside diameter, wall thickness, and metric DN equivalents.
Covers Schedule 40 and 80 for plumbing and industrial use.
Select a pipe size to see all equivalent measurements.
Pipe sizes use nominal names that do NOT match actual dimensions.
NPS (Nominal Pipe Size) is the North American standard (in inches). DN (Diamètre Nominal) is the metric equivalent (in mm). OD (Outside Diameter) is the actual measured outer diameter.
NPS to DN and OD reference:
| NPS | DN | OD (inches) | OD (mm) |
|---|---|---|---|
| 1/8" | DN6 | 0.405" | 10.29 mm |
| 1/4" | DN8 | 0.540" | 13.72 mm |
| 3/8" | DN10 | 0.675" | 17.15 mm |
| 1/2" | DN15 | 0.840" | 21.34 mm |
| 3/4" | DN20 | 1.050" | 26.67 mm |
| 1" | DN25 | 1.315" | 33.40 mm |
| 1-1/4" | DN32 | 1.660" | 42.16 mm |
| 1-1/2" | DN40 | 1.900" | 48.26 mm |
| 2" | DN50 | 2.375" | 60.33 mm |
| 3" | DN80 | 3.500" | 88.90 mm |
| 4" | DN100 | 4.500" | 114.30 mm |
| 6" | DN150 | 6.625" | 168.28 mm |
| 8" | DN200 | 8.625" | 219.08 mm |
NPS 1/8" through 12" does NOT equal the OD. For NPS 14" and above, NPS equals the OD in inches.
How we build and check this converter
This converter runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
SuperGlobalCalculator is independently built and maintained. See how we build and verify our calculators.