Conversion table for nominal pipe sizes DN to the designation in inches, from 6 mm to 600 mm and from 1/8 inch to 24 inches. The nominal pipe size DN (Diameter Nominal) is a value giving the approximate internal diameter of the pipe in mm.
| NOMINAL SIZE | |||||||
| DN | DN | DN | DN | ||||
| [mm] | ["] | [mm] | ["] | [mm] | ["] | [mm] | ["] |
| 6 | 1/8 | 32 | 1 1/4 | 125 | 5 | 400 | 16 |
| 8 | 1/4 | 40 | 1 1/2 | 150 | 6 | 450 | 18 |
| 10 | 3/8 | 50 | 2 | 200 | 8 | 500 | 20 |
| 15 | 1/2 | 65 | 2 1/2 | 250 | 10 | 600 | 24 |
| 20 | 3/4 | 80 | 3 | 300 | 12 | ||
| 25 | 1 | 100 | 4 | 350 | 15 | ||