How it works
DN (diameter nominal) and NPS (Nominal Pipe Size) are only nominal sizes: the outside diameter is fixed for each size, and the inside diameter depends on wall thickness. From 14″ (DN 350) up, NPS equals the outside diameter in inches; below that it does not.
Formula
ID = OD − 2·t m = 0.02466 · (OD − t) · t [kg/m, steel]
Wall thickness is given by the schedule number (Sch 10S, 40, 80, 160 …); STD and XS are older designations that equal Sch 40 and Sch 80 for smaller sizes. The 10S series comes from B36.19M for stainless pipe. Metric pipes to EN 10220 may differ slightly in outside diameter.
Chart
| NPS | DN | OD mm | Sch 10S | Sch 40 | Sch 80 | Sch 160 | XXS |
|---|---|---|---|---|---|---|---|
| 1/8″ | 6 | 10.3 | 1.24 | 1.73 | 2.41 | – | – |
| 1/4″ | 8 | 13.7 | 1.65 | 2.24 | 3.02 | – | – |
| 3/8″ | 10 | 17.1 | 1.65 | 2.31 | 3.20 | – | – |
| 1/2″ | 15 | 21.3 | 2.11 | 2.77 | 3.73 | 4.78 | 7.47 |
| 3/4″ | 20 | 26.7 | 2.11 | 2.87 | 3.91 | 5.56 | 7.82 |
| 1″ | 25 | 33.4 | 2.77 | 3.38 | 4.55 | 6.35 | 9.09 |
| 1 1/4″ | 32 | 42.2 | 2.77 | 3.56 | 4.85 | 6.35 | 9.70 |
| 1 1/2″ | 40 | 48.3 | 2.77 | 3.68 | 5.08 | 7.14 | 10.15 |
| 2″ | 50 | 60.3 | 2.77 | 3.91 | 5.54 | 8.74 | 11.07 |
| 2 1/2″ | 65 | 73.0 | 3.05 | 5.16 | 7.01 | 9.53 | 14.02 |
| 3″ | 80 | 88.9 | 3.05 | 5.49 | 7.62 | 11.13 | 15.24 |
| 3 1/2″ | 90 | 101.6 | 3.05 | 5.74 | 8.08 | – | – |
| 4″ | 100 | 114.3 | 3.05 | 6.02 | 8.56 | 13.49 | 17.12 |
| 5″ | 125 | 141.3 | 3.40 | 6.55 | 9.53 | 15.88 | 19.05 |
| 6″ | 150 | 168.3 | 3.40 | 7.11 | 10.97 | 18.26 | 21.95 |
| 8″ | 200 | 219.1 | 3.76 | 8.18 | 12.70 | 23.01 | – |
| 10″ | 250 | 273.0 | 4.19 | 9.27 | 15.09 | 28.58 | – |
| 12″ | 300 | 323.8 | 4.57 | 10.31 | 17.48 | 33.32 | – |
| 14″ | 350 | 355.6 | – | 11.13 | 19.05 | 35.71 | – |
| 16″ | 400 | 406.4 | – | 12.70 | 21.44 | 40.49 | – |
| 18″ | 450 | 457.0 | – | 14.27 | 23.83 | 45.24 | – |
| 20″ | 500 | 508.0 | – | 15.09 | 26.19 | 50.01 | – |
| 24″ | 600 | 610.0 | – | 17.48 | 30.96 | 59.54 | – |
Wall thickness in mm, ASME B36.10M / B36.19M.
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