Converter
Everything below is plain HTML — copy the tables straight into your own documents. Conversions use 1 bar = 14.5038 psi and 1 inch = 25.4 mm.
DN to inches and NPS
| DN | NPS | Inch | Millimetre |
|---|---|---|---|
| DN15 | NPS ½ | 1/2" | 15 |
| DN20 | NPS ¾ | 3/4" | 20 |
| DN25 | NPS 1 | 1" | 25 |
| DN32 | NPS 1¼ | 1-1/4" | 32 |
| DN40 | NPS 1½ | 1-1/2" | 40 |
| DN50 | NPS 2 | 2" | 50 |
| DN65 | NPS 2½ | 2-1/2" | 65 |
| DN80 | NPS 3 | 3" | 80 |
| DN100 | NPS 4 | 4" | 100 |
| DN125 | NPS 5 | 5" | 125 |
| DN150 | NPS 6 | 6" | 150 |
| DN200 | NPS 8 | 8" | 200 |
| DN250 | NPS 10 | 10" | 250 |
| DN300 | NPS 12 | 12" | 300 |
| DN350 | NPS 14 | 14" | 350 |
| DN400 | NPS 16 | 16" | 400 |
| DN450 | NPS 18 | 18" | 450 |
| DN500 | NPS 20 | 20" | 500 |
| DN600 | NPS 24 | 24" | 600 |
DN and NPS are nominal designations, not measurable dimensions. DN50 and 2" describe the same pipe size class, but the actual bore and the pipe outside diameter are not 50 mm and not 50.8 mm. Do not derive a gasket or flange dimension from this column pair — take those from the flange standard.
PN to bar and psi
| PN | bar | psi | Typical nearest ASME class |
|---|---|---|---|
| PN2.5 | 2.5 | 36 | — |
| PN6 | 6 | 87 | Class 150 (see note) |
| PN10 | 10 | 145 | Class 150 (see note) |
| PN16 | 16 | 232 | Class 150 / 300 |
| PN25 | 25 | 363 | Class 300 |
| PN40 | 40 | 580 | Class 300 |
| PN63 | 63 | 914 | Class 600 |
| PN100 | 100 | 1450 | Class 600 |
PN is a single number valid at 20 °C reference temperature. Above that, the allowable pressure falls — and how far it falls depends on the body material, not on the PN number.
Is PN16 the same as Class 150? No.
This is the most expensive misunderstanding in valve procurement, so it is worth two minutes.
PN (from EN 1333 / ISO 7268) is a round-number metric pressure class. ASME Class (150, 300, 600…) is a pressure–temperature rating table: the number is not a pressure at all. A Class 150 valve made of carbon steel holds about 19.6 bar at 20 °C, about 13.8 bar at 100 °C and less as temperature rises. PN16 holds 16 bar up to its reference temperature.
Worse, the two systems use different flange drilling: EN 1092-2 PN10 has a different bolt circle and bolt count from ASME B16.5 Class 150 at the same DN. A valve that is dimensionally correct for one will not bolt up to the other.
- Buying to a European specification (EN 593, EN 558, EN 1092-2)? Order by PN.
- Buying to an American specification (API 609, ASME B16.5, ASME B16.34)? Order by Class.
- Mixing them requires a flange adapter or a spool piece — and someone has to pay for it.
So when you send an enquiry, the single most useful line you can add is the flange standard: "EN 1092-2 PN16" or "ASME B16.5 Class 150". It removes the one item we otherwise have to ask about before quoting.
What we supply
- Wafer and lug butterfly valves, DN50–DN1200, body in ductile iron GGG50, WCB, CF8 or CF8M.
- PN10 and PN16 as standard, with PN25 on request; ASME Class 150 drilling available on the same body for the American market.
- Seats in EPDM, NBR, PTFE and wear-resistant rubber; discs in ductile iron, SS304 or SS316, with nylon-coated and hard-chrome options for abrasive duty.
- Hand lever, gearbox, and pneumatic actuation (double acting or spring-return fail-safe) with solenoid valve and limit switch box.
Not sure which size and rating you need? Send the line size, the medium and the working pressure — we will come back with the model and the price.
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Frequently asked questions
What is DN100 in inches?
DN100 is a 4" (NPS 4) nominal size. DN and NPS are two names for the same size class — they are nominal designations, so the actual bore is not exactly 100 mm and not exactly 101.6 mm.
What does PN16 mean?
PN16 means a nominal pressure rating of 16 bar (about 232 psi) at the 20 °C reference temperature, following EN 1333. It is the most common rating for general water, HVAC and utility butterfly valves in Europe, the Middle East and Africa.
Is PN16 the same as 150 lb?
No. Class 150 is a pressure–temperature rating table, not a pressure: a carbon steel Class 150 valve is rated about 19.6 bar at 20 °C but only about 13.8 bar at 100 °C. The flange drilling of EN 1092-2 PN16 and ASME B16.5 Class 150 is also different, so the two do not bolt together.
How many psi is PN10 and PN16?
PN10 is 10 bar, which is 145 psi. PN16 is 16 bar, which is 232 psi. Convert any PN value with 1 bar = 14.5038 psi.
What is the difference between DN and NPS?
DN (diamètre nominal) is the metric designation used by EN and ISO standards; NPS (nominal pipe size) is the inch designation used by ASME. DN50 and NPS 2 describe the same size class.
Can I use this table for flange dimensions?
No. It only maps size and pressure designations. Bolt circle, bolt count, bolt hole diameter and flange thickness come from the flange standard you are buying to — EN 1092-2, ASME B16.5, AS2129, JIS B2220 and so on. Tell us which one applies and we will confirm the drilling.