Table
Knockout Hole Size by Conduit Trade Size
Knockout Hole Size by Conduit Trade Size lookup table with assumptions and boundary notes.
Scope
Dimensional planning planning only. Enclosure drawings, fitting instructions, listings, and manufacturer templates govern actual openings.
Lookup table
Lookup common nominal knockout and punch diameters for conduit trade-size planning.
Scroll sideways to keep row labels aligned with hidden columns.
| 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 |
Notes
- Check table values for preliminary lookup and arithmetic checks only.
- Confirm equipment ratings, product markings, installation conditions, utility requirements, and the local authority requirements before design or field use.