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.