Pipe Dimensions Reference
Complete pipe dimension table — nominal size, outside diameter, inside diameter, wall thickness, and weight per metre for all common pipe sizes and schedules.
DN vs NPS
DN (Diamètre Nominal) is the metric designation used in international (ISO) standards. NPS (Nominal Pipe Size) is the imperial designation used in North America. Neither DN nor NPS exactly matches the actual outside diameter — they are nominal sizes for reference.
Example: DN50 (NPS 2") has an actual outside diameter of 60.3 mm, not 50 mm or 2 inches (50.8 mm).
Common Pipe Dimensions (Sch 40)
| DN | NPS | OD (mm) | ID (mm) | WT (mm) | Weight (kg/m) |
|---|---|---|---|---|---|
| 15 | 1/2" | 21.3 | 15.8 | 2.77 | 1.27 |
| 20 | 3/4" | 26.7 | 21.0 | 2.87 | 1.69 |
| 25 | 1" | 33.4 | 26.6 | 3.38 | 2.50 |
| 32 | 1 1/4" | 42.2 | 35.1 | 3.56 | 3.39 |
| 40 | 1 1/2" | 48.3 | 40.9 | 3.68 | 4.05 |
| 50 | 2" | 60.3 | 52.5 | 3.91 | 5.44 |
| 65 | 2 1/2" | 76.1 | 62.7 | 5.16 | 8.29 |
| 80 | 3" | 88.9 | 77.9 | 5.49 | 11.29 |
| 100 | 4" | 114.3 | 102.3 | 6.02 | 16.07 |
| 150 | 6" | 168.3 | 154.1 | 7.11 | 28.26 |
Why nominal size ≠ OD
Pipe sizes originated in the early days when the nominal size was approximately the inside diameter of standard wall pipe. As wall thicknesses standardised, the OD became fixed but the nominal name stuck. This is why a '2-inch pipe' has an OD of 60.3 mm (2.375 inches), not 2 inches.
How CHI can help
Ask CHI about pipe dimensions and to look up inside diameters for flow and pressure drop calculations. The CHI assistant can look up specific values, explain what each table entry means, and help you cross-reference between different standards and unit systems.