2-1/2-inch IMC Conduit Fill
Wire capacity of trade size 2-1/2 (metric designator 63) Intermediate Metal Conduit, for THHN, XHHW, THW and RHW conductors from 14 AWG to 1000 kcmil.
2-1/2-inch IMC holds 97 × #10, 56 × #8, 40 × #6 or 25 × #4 THHN conductors at 40% fill. Internal area: 5.135 in²; usable at 40%: 2.054 in².
| Wire size | THHN | XHHW | THW | RHW | THHN in a nipple (60%) | THHN area (in²) |
|---|---|---|---|---|---|---|
| 14 AWG | 211 | 147 | 147 | 70 | 317 | 0.0097 |
| 12 AWG | 154 | 113 | 113 | 58 | 231 | 0.0133 |
| 10 AWG | 97 | 84 | 84 | 47 | 146 | 0.0211 |
| 8 AWG | 56 | 47 | 47 | 24 | 84 | 0.0366 |
| 6 AWG | 40 | 35 | 28 | 19 | 60 | 0.0507 |
| 4 AWG | 25 | 25 | 21 | 15 | 37 | 0.0824 |
| 3 AWG | 21 | 21 | 18 | 13 | 31 | 0.0973 |
| 2 AWG | 17 | 18 | 15 | 11 | 26 | 0.1158 |
| 1 AWG | 13 | 13 | 11 | 7 | 19 | 0.1562 |
| 1/0 AWG | 11 | 11 | 9 | 6 | 16 | 0.1855 |
| 2/0 AWG | 9 | 9 | 8 | 6 | 14 | 0.2223 |
| 3/0 AWG | 7 | 7 | 6 | 5 | 11 | 0.2679 |
| 4/0 AWG | 6 | 6 | 5 | 4 | 9 | 0.3237 |
| 250 kcmil | 5 | 5 | 4 | 3 | 7 | 0.3970 |
| 300 kcmil | 4 | 4 | 4 | 3 | 6 | 0.4608 |
| 350 kcmil | 4 | 4 | 3 | 2 | 6 | 0.5242 |
| 400 kcmil | 3 | 3 | 3 | 1 | 5 | 0.5863 |
| 500 kcmil | 3 | 3 | 2 | 1 | 4 | 0.7073 |
| 600 kcmil | 1 | 1 | 1 | 1 | 3 | 0.8676 |
| 700 kcmil | 1 | 1 | 1 | 1 | 3 | 0.9887 |
| 750 kcmil | 1 | 1 | 1 | 1 | 3 | 1.0496 |
| 800 kcmil | 1 | 1 | 1 | 1 | 2 | 1.1085 |
| 900 kcmil | 1 | 1 | 1 | 1 | 2 | 1.2311 |
| 1000 kcmil | 1 | 1 | 1 | 1 | 2 | 1.3478 |
Mixed wire sizes? Calculate it
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2-1/2-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 | 2.731 | 5.858 | 2.343 | 176 | 111 | 46 |
| PVC Schedule 40 | 2.445 | 4.695 | 1.878 | 141 | 89 | 37 |
| PVC Schedule 80 | 2.290 | 4.119 | 1.648 | 124 | 78 | 32 |
| Rigid Metal Conduit | 2.489 | 4.866 | 1.946 | 146 | 92 | 38 |
| IMC | 2.557 | 5.135 | 2.054 | 154 | 97 | 40 |
| Flexible Metal Conduit | 2.500 | 4.909 | 1.964 | 147 | 93 | 38 |
| Liquidtight Flexible Metal Conduit | 2.493 | 4.881 | 1.952 | 146 | 92 | 38 |
Other IMC sizes
Frequently asked questions
How many #12 wires fit in 2-1/2-inch IMC?
154 conductors of 12 AWG THHN/THWN-2 at the 40% fill limit. With thicker THW or XHHW insulation the count is 113.
What is the inside diameter and area of 2-1/2-inch IMC?
The internal diameter is 2.557 in. (64.9 mm) and the total cross-sectional area is 5.135 in². The usable area is 2.054 in² at 40% fill, 1.592 in² for two wires and 2.722 in² for one.
What is the largest wire I can pull three of in 2-1/2-inch IMC?
500 kcmil 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 154 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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