3/8-inch Flexible Metal (FMC) Conduit Fill
Wire capacity of trade size 3/8 (metric designator 12) Flexible Metal Conduit (FMC), for THHN, XHHW, THW and RHW conductors from 14 AWG to 1000 kcmil.
3/8-inch Flexible Metal Conduit holds 4 × #14, 3 × #12, 1 × #10 or 1 × #8 THHN conductors at 40% fill. Internal area: 0.116 in²; usable at 40%: 0.046 in².
| Wire size | THHN | XHHW | THW | RHW | THHN in a nipple (60%) | THHN area (in²) |
|---|---|---|---|---|---|---|
| 14 AWG | 4 | 3 | 3 | 1 | 7 | 0.0097 |
| 12 AWG | 3 | 1 | 1 | 1 | 5 | 0.0133 |
| 10 AWG | 1 | 1 | 1 | 1 | 3 | 0.0211 |
| 8 AWG | 1 | 1 | 1 | — | 2 | 0.0366 |
| 6 AWG | 1 | 1 | — | — | 1 | 0.0507 |
| 4 AWG | — | — | — | — | 1 | 0.0824 |
| 3 AWG | — | — | — | — | — | 0.0973 |
| 2 AWG | — | — | — | — | — | 0.1158 |
| 1 AWG | — | — | — | — | — | 0.1562 |
| 1/0 AWG | — | — | — | — | — | 0.1855 |
| 2/0 AWG | — | — | — | — | — | 0.2223 |
| 3/0 AWG | — | — | — | — | — | 0.2679 |
| 4/0 AWG | — | — | — | — | — | 0.3237 |
| 250 kcmil | — | — | — | — | — | 0.3970 |
| 300 kcmil | — | — | — | — | — | 0.4608 |
| 350 kcmil | — | — | — | — | — | 0.5242 |
| 400 kcmil | — | — | — | — | — | 0.5863 |
| 500 kcmil | — | — | — | — | — | 0.7073 |
| 600 kcmil | — | — | — | — | — | 0.8676 |
| 700 kcmil | — | — | — | — | — | 0.9887 |
| 750 kcmil | — | — | — | — | — | 1.0496 |
| 800 kcmil | — | — | — | — | — | 1.1085 |
| 900 kcmil | — | — | — | — | — | 1.2311 |
| 1000 kcmil | — | — | — | — | — | 1.3478 |
Mixed wire sizes? Calculate it
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3/8-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 |
|---|---|---|---|---|---|---|
| Flexible Metal Conduit | 0.384 | 0.116 | 0.046 | 3 | 1 | 1 |
| Liquidtight Flexible Metal Conduit | 0.494 | 0.192 | 0.077 | 5 | 3 | 1 |
Other Flexible Metal Conduit sizes
Frequently asked questions
How many #12 wires fit in 3/8-inch Flexible Metal Conduit?
3 conductors of 12 AWG THHN/THWN-2 at the 40% fill limit. With thicker THW or XHHW insulation the count is 1.
What is the inside diameter and area of 3/8-inch Flexible Metal Conduit?
The internal diameter is 0.384 in. (9.8 mm) and the total cross-sectional area is 0.116 in². The usable area is 0.046 in² at 40% fill, 0.036 in² for two wires and 0.061 in² for one.
What is the largest wire I can pull three of in 3/8-inch Flexible Metal Conduit?
12 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.
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