Table
Knockout Hole Size by Conduit Trade Size
Knockout Hole Size by Conduit Trade Size reference with assumptions and boundary notes.
Reference boundary
Dimensional planning reference only. Enclosure drawings, fitting instructions, listings, and manufacturer templates govern actual openings.
Reference table
Reference common nominal knockout and punch diameters for conduit trade-size planning.
| Conduit trade size | Nominal KO diameter (in) | Nominal KO diameter (mm) | Common punch label | Boundary |
|---|---|---|---|---|
| 1/2 in | 0.875 | 22.2 | 1/2 in conduit knockout | Confirm the actual enclosure drawing, fitting, and punch system before layout |
| 3/4 in | 1.109 | 28.2 | 3/4 in conduit knockout | Confirm the actual enclosure drawing, fitting, and punch system before layout |
| 1 in | 1.375 | 34.9 | 1 in conduit knockout | Confirm the actual enclosure drawing, fitting, and punch system before layout |
| 1-1/4 in | 1.734 | 44 | 1-1/4 in conduit knockout | Confirm the actual enclosure drawing, fitting, and punch system before layout |
| 1-1/2 in | 1.984 | 50.4 | 1-1/2 in conduit knockout | Confirm the actual enclosure drawing, fitting, and punch system before layout |
| 2 in | 2.469 | 62.7 | 2 in conduit knockout | Confirm the actual enclosure drawing, fitting, and punch system before layout |
| 2-1/2 in | 2.969 | 75.4 | 2-1/2 in conduit knockout | Confirm the actual enclosure drawing, fitting, and punch system before layout |
| 3 in | 3.594 | 91.3 | 3 in conduit knockout | Confirm the actual enclosure drawing, fitting, and punch system before layout |
| 3-1/2 in | 4.094 | 104 | 3-1/2 in conduit knockout | Confirm the actual enclosure drawing, fitting, and punch system before layout |
| 4 in | 4.594 | 116.7 | 4 in conduit knockout | Confirm the actual enclosure drawing, fitting, and punch system before layout |
Use notes
- Use this table for preliminary reference and arithmetic checks only.
- Confirm equipment ratings, product markings, installation conditions, utility requirements, and the local authority requirements before design or field use.