| Data from: Steel Tube Institute of North America | |
| Table 1: Metric Trade Size Designators | |
| For RMC, IMC and EMT conduit | |
| *Trade Size Designator |
|
| English (inch) | Metric (mm) |
| 1/2 | 16 |
| 3/4 | 21 |
| 1 | 27 |
| 1 1/4 | 35 |
| 1 1/2 | 41 |
| 2 | 53 |
| 2 1/2 | 63 |
| 3 | 78 |
| 3 1/2 | 91 |
| 4 | 103 |
| 5 | 129 |
| 6 | 155 |
| * Identifier only; not an actual dimension | |
| Rigid metal conduit — RMC (ferrous metal) | |
| Intermediate metal conduit - IMC (ferrous metal) | |
| Electrical metallic tubing - EMT (ferrous metal) | |