DN ↔ NPS / Inch Conversion
Quick nominal pipe size reference between metric DN and imperial NPS.
Approximate nominal pipe size conversion between metric DN and imperial NPS. The OD shown is the typical pipe outside diameter used for common steel pipe sizes.
| DN | NPS / Inch | Typical OD [mm] |
|---|---|---|
| DN15 | 1/2" | 21.3 |
| DN20 | 3/4" | 26.7 |
| DN25 | 1" | 33.4 |
| DN32 | 1 1/4" | 42.2 |
| DN40 | 1 1/2" | 48.3 |
| DN50 | 2" | 60.3 |
| DN65 | 2 1/2" | 73.0 |
| DN80 | 3" | 88.9 |
| DN100 | 4" | 114.3 |
| DN150 | 6" | 168.3 |
| DN200 | 8" | 219.1 |
| DN250 | 10" | 273.0 |
| DN300 | 12" | 323.9 |
| DN350 | 14" | 355.6 |
| DN400 | 16" | 406.4 |
| DN450 | 18" | 457.0 |
| DN500 | 20" | 508.0 |
| DN600 | 24" | 609.6 |
Important note
DN and NPS are nominal size systems. They are not direct physical diameter values. Always verify the applicable pipe standard, schedule/wall thickness and actual outside diameter.