4-inch IMC Conduit Fill
Wire capacity of trade size 4 (metric designator 103) Intermediate Metal Conduit, for THHN, XHHW, THW and RHW conductors from 14 AWG to 1000 kcmil.
4-inch IMC holds 66 × #4, 47 × #2, 29 × 1/0 AWG or 17 × 4/0 AWG THHN conductors at 40% fill. Internal area: 13.631 in²; usable at 40%: 5.452 in².
| Wire size | THHN | XHHW | THW | RHW | THHN in a nipple (60%) | THHN area (in²) |
|---|---|---|---|---|---|---|
| 14 AWG | 562 | 392 | 392 | 186 | 843 | 0.0097 |
| 12 AWG | 410 | 301 | 301 | 154 | 615 | 0.0133 |
| 10 AWG | 258 | 224 | 224 | 124 | 387 | 0.0211 |
| 8 AWG | 149 | 124 | 124 | 65 | 223 | 0.0366 |
| 6 AWG | 107 | 92 | 75 | 52 | 161 | 0.0507 |
| 4 AWG | 66 | 67 | 56 | 41 | 99 | 0.0824 |
| 3 AWG | 56 | 56 | 48 | 36 | 84 | 0.0973 |
| 2 AWG | 47 | 47 | 41 | 31 | 70 | 0.1158 |
| 1 AWG | 35 | 35 | 28 | 20 | 52 | 0.1562 |
| 1/0 AWG | 29 | 30 | 24 | 18 | 44 | 0.1855 |
| 2/0 AWG | 24 | 25 | 20 | 15 | 36 | 0.2223 |
| 3/0 AWG | 20 | 20 | 17 | 13 | 30 | 0.2679 |
| 4/0 AWG | 17 | 17 | 14 | 11 | 25 | 0.3237 |
| 250 kcmil | 13 | 14 | 12 | 8 | 20 | 0.3970 |
| 300 kcmil | 12 | 12 | 10 | 7 | 17 | 0.4608 |
| 350 kcmil | 10 | 10 | 9 | 7 | 15 | 0.5242 |
| 400 kcmil | 9 | 9 | 8 | 6 | 14 | 0.5863 |
| 500 kcmil | 7 | 8 | 7 | 5 | 11 | 0.7073 |
| 600 kcmil | 6 | 6 | 5 | 4 | 9 | 0.8676 |
| 700 kcmil | 5 | 5 | 5 | 4 | 8 | 0.9887 |
| 750 kcmil | 5 | 5 | 4 | 4 | 7 | 1.0496 |
| 800 kcmil | 5 | 5 | 4 | 3 | 7 | 1.1085 |
| 900 kcmil | 4 | 4 | 4 | 3 | 6 | 1.2311 |
| 1000 kcmil | 4 | 4 | 3 | 3 | 6 | 1.3478 |
Mixed wire sizes? Calculate it
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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 | 4.334 | 14.753 | 5.901 | 443 | 279 | 116 |
| PVC Schedule 40 | 3.998 | 12.554 | 5.022 | 377 | 238 | 99 |
| PVC Schedule 80 | 3.786 | 11.258 | 4.503 | 338 | 213 | 89 |
| Rigid Metal Conduit | 4.050 | 12.882 | 5.153 | 387 | 244 | 101 |
| IMC | 4.166 | 13.631 | 5.452 | 410 | 258 | 107 |
| Flexible Metal Conduit | 4.000 | 12.566 | 5.026 | 378 | 238 | 99 |
| Liquidtight Flexible Metal Conduit | 4.020 | 12.692 | 5.077 | 381 | 240 | 100 |
Other IMC sizes
Frequently asked questions
How many #12 wires fit in 4-inch IMC?
410 conductors of 12 AWG THHN/THWN-2 at the 40% fill limit. With thicker THW or XHHW insulation the count is 301.
What is the inside diameter and area of 4-inch IMC?
The internal diameter is 4.166 in. (105.8 mm) and the total cross-sectional area is 13.631 in². The usable area is 5.452 in² at 40% fill, 4.226 in² for two wires and 7.224 in² for one.
What is the largest wire I can pull three of in 4-inch IMC?
1000 kcmil THHN: 4 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 410 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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