Pipe Size Converter
Convert between nominal pipe size (NPS), outside diameter, and metric DN equivalents.
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.