| DN | Inches | OD EN (mm) | OD ASME (mm) | WT Sch 40 (mm) | ID (mm) |
|---|---|---|---|---|---|
| DN6 | 1/8″ | 10.2 | 10.3 | 1.73 | 6.8 |
| DN8 | 1/4″ | 13.5 | 13.7 | 2.24 | 9.2 |
| DN10 | 3/8″ | 17.2 | 17.1 | 2.31 | 12.5 |
| DN15 | 1/2″ | 21.3 | 21.3 | 2.77 | 15.8 |
| DN20 | 3/4″ | 26.9 | 26.7 | 2.87 | 21 |
| DN25 | 1″ | 33.7 | 33.4 | 3.38 | 26.6 |
| DN32 | 1 1/4″ | 42.4 | 42.2 | 3.56 | 35.1 |
| DN40 | 1 1/2″ | 48.3 | 48.3 | 3.68 | 40.9 |
| DN50 | 2″ | 60.3 | 60.3 | 3.91 | 52.5 |
| DN65 | 2 1/2″ | 76.1 | 73 | 5.16 | 62.7 |
| DN80 | 3″ | 88.9 | 88.9 | 5.49 | 77.9 |
| DN90 | 3 1/2″ | 101.6 | 101.6 | 5.74 | 90.1 |
| DN100 | 4″ | 114.3 | 114.3 | 6.02 | 102.3 |
| DN125 | 5″ | 139.7 | 141.3 | 6.55 | 128.2 |
| DN150 | 6″ | 168.3 | 168.3 | 7.11 | 154.1 |
| DN200 | 8″ | 219.1 | 219.1 | 8.18 | 202.7 |
| DN250 | 10″ | 273 | 273.1 | 9.27 | 254.6 |
| DN300 | 12″ | 323.9 | 323.8 | 10.31 | 303.2 |
| DN350 | 14″ | 355.6 | 355.6 | 11.13 | 333.3 |
| DN400 | 16″ | 406.4 | 406.4 | 12.7 | 381 |
| DN450 | 18″ | 457 | 457 | 14.27 | 428.5 |
| DN500 | 20″ | 508 | 508 | 15.09 | 477.8 |
| DN600 | 24″ | 610 | 610 | 17.48 | 575 |
| DN700 | 28″ | 711 | 711 | — | — |
| DN750 | 30″ | 762 | 762 | — | — |
| DN800 | 32″ | 813 | 813 | — | — |
| DN900 | 36″ | 914 | 914 | — | — |
| DN1000 | 40″ | 1,016 | 1,016 | — | — |
| DN1200 | 48″ | 1,219 | 1,219 | — | — |
| DN1400 | 56″ | 1,422 | 1,422 | — | — |
| DN1600 | 64″ | 1,626 | 1,626 | — | — |
| DN1800 | 72″ | 1,829 | 1,829 | — | — |
OD EN — metric pipes per EN 10220 / EN ISO 1127. OD ASME, Sch 40 wall and inside diameter — inch pipes per ASME B36.10M / B36.19M (up to NPS 10 Sch 40S has the same wall). Approximate values.
DN is a label, not a measurement
DN (nominal diameter) identifies a size class. It does not give you millimetres. A DN50 pipe is not 50 mm across — the real outside diameter depends on the standard the pipe was made to, and that is the number that decides whether a fitting slides on.
Why one DN gives several diameters
In our own stock, DN25 turns up as 33.7, 33.4, 32, 31.8 and 30 mm. The split runs between the European series (EN 10220, EN ISO 1127) and the American one (ASME B36.10M, B36.19M). DN65 is the clearest case: 76.1 mm to EN, 73.0 mm to ASME. Three millimetres decide whether the joint closes.
The calculator above returns both, so you can match whichever series your drawing refers to instead of guessing.
OD, WT and ID
- OD — outside diameter. The figure that decides whether a fitting, flange or clamp fits.
- WT — wall thickness, usually given as a schedule (Sch 10S, Sch 40S). The same DN in a heavier schedule keeps its OD and loses bore.
- ID — inside diameter: OD minus twice the wall. This is what actually carries the flow, and it is the number a pressure-drop calculation needs.
Ordering from us
Give us the DN and the standard, or simply the outside diameter and wall in millimetres — either is enough. If your drawing quotes inches, the calculator converts it. Everything we list is stainless: acid-resistant, heat-resistant, duplex and the austenitic grades.