1-1/4-inch IMC Conduit Fill
Wire capacity of trade size 1-1/4 (metric designator 35) Intermediate Metal Conduit, for THHN, XHHW, THW and RHW conductors from 14 AWG to 1000 kcmil.
1-1/4-inch IMC holds 68 × #14, 49 × #12, 31 × #10 or 18 × #8 THHN conductors at 40% fill. Internal area: 1.647 in²; usable at 40%: 0.659 in².
| Wire size | THHN | XHHW | THW | RHW | THHN in a nipple (60%) | THHN area (in²) |
|---|---|---|---|---|---|---|
| 14 AWG | 68 | 47 | 47 | 22 | 102 | 0.0097 |
| 12 AWG | 49 | 36 | 36 | 18 | 74 | 0.0133 |
| 10 AWG | 31 | 27 | 27 | 15 | 47 | 0.0211 |
| 8 AWG | 18 | 15 | 15 | 8 | 27 | 0.0366 |
| 6 AWG | 13 | 11 | 9 | 6 | 19 | 0.0507 |
| 4 AWG | 8 | 8 | 6 | 5 | 12 | 0.0824 |
| 3 AWG | 6 | 7 | 6 | 4 | 10 | 0.0973 |
| 2 AWG | 5 | 5 | 5 | 3 | 8 | 0.1158 |
| 1 AWG | 4 | 4 | 3 | 1 | 6 | 0.1562 |
| 1/0 AWG | 3 | 3 | 3 | 1 | 5 | 0.1855 |
| 2/0 AWG | 3 | 3 | 1 | 1 | 4 | 0.2223 |
| 3/0 AWG | 1 | 1 | 1 | 1 | 3 | 0.2679 |
| 4/0 AWG | 1 | 1 | 1 | 1 | 3 | 0.3237 |
| 250 kcmil | 1 | 1 | 1 | 1 | 2 | 0.3970 |
| 300 kcmil | 1 | 1 | 1 | 1 | 2 | 0.4608 |
| 350 kcmil | 1 | 1 | 1 | 1 | 2 | 0.5242 |
| 400 kcmil | 1 | 1 | 1 | 1 | 1 | 0.5863 |
| 500 kcmil | 1 | 1 | 1 | — | 1 | 0.7073 |
| 600 kcmil | 1 | 1 | — | — | 1 | 0.8676 |
| 700 kcmil | — | — | — | — | 1 | 0.9887 |
| 750 kcmil | — | — | — | — | 1 | 1.0496 |
| 800 kcmil | — | — | — | — | 1 | 1.1085 |
| 900 kcmil | — | — | — | — | 1 | 1.2311 |
| 1000 kcmil | — | — | — | — | — | 1.3478 |
Mixed wire sizes? Calculate it
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1-1/4-inch conduit: IMC vs other types
Trade size is nominal. The real inside diameter, and so the wire count, changes with the wall thickness of each raceway type.
| Conduit type | ID (in) | Area (in²) | 40% (in²) | #12 THHN | #10 THHN | #6 THHN |
|---|---|---|---|---|---|---|
| EMT | 1.380 | 1.496 | 0.598 | 45 | 28 | 12 |
| PVC Schedule 40 | 1.360 | 1.453 | 0.581 | 43 | 27 | 11 |
| PVC Schedule 80 | 1.255 | 1.237 | 0.495 | 37 | 23 | 9 |
| Rigid Metal Conduit | 1.394 | 1.526 | 0.610 | 46 | 29 | 12 |
| IMC | 1.448 | 1.647 | 0.659 | 49 | 31 | 13 |
| Flexible Metal Conduit | 1.275 | 1.277 | 0.511 | 38 | 24 | 10 |
| Liquidtight Flexible Metal Conduit | 1.395 | 1.528 | 0.611 | 46 | 29 | 12 |
| ENT | 1.360 | 1.453 | 0.581 | 43 | 27 | 11 |
Other IMC sizes
Frequently asked questions
How many #12 wires fit in 1-1/4-inch IMC?
49 conductors of 12 AWG THHN/THWN-2 at the 40% fill limit. With thicker THW or XHHW insulation the count is 36.
What is the inside diameter and area of 1-1/4-inch IMC?
The internal diameter is 1.448 in. (36.8 mm) and the total cross-sectional area is 1.647 in². The usable area is 0.659 in² at 40% fill, 0.511 in² for two wires and 0.873 in² for one.
What is the largest wire I can pull three of in 1-1/4-inch IMC?
2/0 AWG THHN: 3 conductors fit at 40% fill. That is three current-carrying conductors with no ground; add the ground’s area and check again with the calculator if you need one.
Can I really load it with that many conductors?
For space, yes. But 49 current-carrying conductors in one raceway means heavy ampacity derating — 10 to 20 conductors are adjusted to 50% of their table ampacity. Fill tells you what fits; derating tells you what it can carry.
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