If you buy valves internationally, you will see sizes written two ways: DN (metric) and inch (imperial), plus pressure as PN or Class. This quick-reference chart helps you convert and specify correctly on your RFQ.
DN to Inch Conversion
Nominal diameter (DN) is the metric size; NPS (inch) is the imperial size. They refer to the same pipe bore:
| DN | Inch | DN | Inch |
|---|---|---|---|
| DN50 | 2" | DN300 | 12" |
| DN65 | 2.5" | DN350 | 14" |
| DN80 | 3" | DN400 | 16" |
| DN100 | 4" | DN500 | 20" |
| DN125 | 5" | DN600 | 24" |
| DN150 | 6" | DN800 | 32" |
| DN200 | 8" | DN1000 | 40" |
| DN250 | 10" | DN1200 | 48" |
PN vs Class Pressure Ratings
PN (Pressure Nominal) is the metric rating in bar; Class is the imperial rating in psi. Common equivalents:
| PN | Class (approx.) | Working pressure |
|---|---|---|
| PN6 | Class 75 | 6 bar |
| PN10 | Class 125 | 10 bar |
| PN16 | Class 150 | 16 bar |
| PN25 | Class 300 | 25 bar |
| PN40 | Class 300 | 40 bar |
Note: PN and Class are not exact equivalents — always confirm with the flange standard (EN 1092 vs ASME B16.5).
How to Read a Valve Size on an RFQ
When you see "DN200 PN16 wafer butterfly valve", it means: nominal bore 200 mm, pressure rating 16 bar, wafer end connection. When you see "8 inch Class 150 lug butterfly valve", it means: 8-inch bore, Class 150 rating, lug connection. State both systems when possible to avoid errors.
What Reguvale Supplies
We manufacture wafer butterfly valves in DN50–DN1200 (2"–48") with PN10/PN16 ratings, in ductile iron, carbon steel and stainless steel. Send us your size and we’ll confirm availability and delivery.