2-1/2-inch Flexible Metal (FMC) Conduit Fill
Wire capacity of trade size 2-1/2 (metric designator 63) Flexible Metal Conduit (FMC), for THHN, XHHW, THW and RHW conductors from 14 AWG to 1000 kcmil.
2-1/2-inch Flexible Metal Conduit holds 93 × #10, 53 × #8, 38 × #6 or 24 × #4 THHN conductors at 40% fill. Internal area: 4.909 in²; usable at 40%: 1.964 in².
| Wire size | THHN | XHHW | THW | RHW | THHN in a nipple (60%) | THHN area (in²) |
|---|---|---|---|---|---|---|
| 14 AWG | 202 | 141 | 141 | 67 | 303 | 0.0097 |
| 12 AWG | 147 | 108 | 108 | 55 | 221 | 0.0133 |
| 10 AWG | 93 | 81 | 81 | 45 | 139 | 0.0211 |
| 8 AWG | 53 | 45 | 45 | 23 | 80 | 0.0366 |
| 6 AWG | 38 | 33 | 27 | 19 | 58 | 0.0507 |
| 4 AWG | 24 | 24 | 20 | 14 | 35 | 0.0824 |
| 3 AWG | 20 | 20 | 17 | 13 | 30 | 0.0973 |
| 2 AWG | 17 | 17 | 14 | 11 | 25 | 0.1158 |
| 1 AWG | 12 | 13 | 10 | 7 | 19 | 0.1562 |
| 1/0 AWG | 10 | 10 | 9 | 6 | 16 | 0.1855 |
| 2/0 AWG | 9 | 9 | 7 | 5 | 13 | 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 | 3 | 2 | 6 | 0.4608 |
| 350 kcmil | 3 | 4 | 3 | 1 | 5 | 0.5242 |
| 400 kcmil | 3 | 3 | 3 | 1 | 5 | 0.5863 |
| 500 kcmil | 2 | 3 | 1 | 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: Flexible Metal Conduit 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 Flexible Metal Conduit sizes
Frequently asked questions
How many #12 wires fit in 2-1/2-inch Flexible Metal Conduit?
147 conductors of 12 AWG THHN/THWN-2 at the 40% fill limit. With thicker THW or XHHW insulation the count is 108.
What is the inside diameter and area of 2-1/2-inch Flexible Metal Conduit?
The internal diameter is 2.500 in. (63.5 mm) and the total cross-sectional area is 4.909 in². The usable area is 1.964 in² at 40% fill, 1.522 in² for two wires and 2.602 in² for one.
What is the largest wire I can pull three of in 2-1/2-inch Flexible Metal Conduit?
400 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 147 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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