3-inch Flexible Metal (FMC) Conduit Fill
Wire capacity of trade size 3 (metric designator 78) Flexible Metal Conduit (FMC), for THHN, XHHW, THW and RHW conductors from 14 AWG to 1000 kcmil.
3-inch Flexible Metal Conduit holds 77 × #8, 55 × #6, 34 × #4 or 24 × #2 THHN conductors at 40% fill. Internal area: 7.069 in²; usable at 40%: 2.828 in².
| Wire size | THHN | XHHW | THW | RHW | THHN in a nipple (60%) | THHN area (in²) |
|---|---|---|---|---|---|---|
| 14 AWG | 291 | 203 | 203 | 96 | 437 | 0.0097 |
| 12 AWG | 212 | 156 | 156 | 80 | 319 | 0.0133 |
| 10 AWG | 134 | 116 | 116 | 64 | 201 | 0.0211 |
| 8 AWG | 77 | 64 | 64 | 34 | 116 | 0.0366 |
| 6 AWG | 55 | 48 | 39 | 27 | 83 | 0.0507 |
| 4 AWG | 34 | 34 | 29 | 21 | 51 | 0.0824 |
| 3 AWG | 29 | 29 | 25 | 18 | 43 | 0.0973 |
| 2 AWG | 24 | 24 | 21 | 16 | 36 | 0.1158 |
| 1 AWG | 18 | 18 | 15 | 10 | 27 | 0.1562 |
| 1/0 AWG | 15 | 15 | 12 | 9 | 23 | 0.1855 |
| 2/0 AWG | 12 | 13 | 10 | 8 | 19 | 0.2223 |
| 3/0 AWG | 10 | 10 | 9 | 7 | 16 | 0.2679 |
| 4/0 AWG | 8 | 9 | 7 | 6 | 13 | 0.3237 |
| 250 kcmil | 7 | 7 | 6 | 4 | 10 | 0.3970 |
| 300 kcmil | 6 | 6 | 5 | 4 | 9 | 0.4608 |
| 350 kcmil | 5 | 5 | 4 | 3 | 8 | 0.5242 |
| 400 kcmil | 5 | 5 | 4 | 3 | 7 | 0.5863 |
| 500 kcmil | 4 | 4 | 3 | 3 | 6 | 0.7073 |
| 600 kcmil | 3 | 3 | 3 | 1 | 5 | 0.8676 |
| 700 kcmil | 3 | 3 | 1 | 1 | 4 | 0.9887 |
| 750 kcmil | 2 | 2 | 1 | 1 | 4 | 1.0496 |
| 800 kcmil | 1 | 1 | 1 | 1 | 4 | 1.1085 |
| 900 kcmil | 1 | 1 | 1 | 1 | 3 | 1.2311 |
| 1000 kcmil | 1 | 1 | 1 | 1 | 3 | 1.3478 |
Mixed wire sizes? Calculate it
Loading calculator…
3-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 | 3.356 | 8.846 | 3.538 | 266 | 167 | 69 |
| PVC Schedule 40 | 3.042 | 7.268 | 2.907 | 218 | 137 | 57 |
| PVC Schedule 80 | 2.864 | 6.442 | 2.577 | 193 | 122 | 51 |
| Rigid Metal Conduit | 3.090 | 7.499 | 3.000 | 225 | 142 | 59 |
| IMC | 3.176 | 7.922 | 3.169 | 238 | 150 | 62 |
| Flexible Metal Conduit | 3.000 | 7.069 | 2.828 | 212 | 134 | 55 |
| Liquidtight Flexible Metal Conduit | 3.085 | 7.475 | 2.990 | 225 | 141 | 59 |
Other Flexible Metal Conduit sizes
Frequently asked questions
How many #12 wires fit in 3-inch Flexible Metal Conduit?
212 conductors of 12 AWG THHN/THWN-2 at the 40% fill limit. With thicker THW or XHHW insulation the count is 156.
What is the inside diameter and area of 3-inch Flexible Metal Conduit?
The internal diameter is 3.000 in. (76.2 mm) and the total cross-sectional area is 7.069 in². The usable area is 2.828 in² at 40% fill, 2.191 in² for two wires and 3.747 in² for one.
What is the largest wire I can pull three of in 3-inch Flexible Metal Conduit?
700 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 212 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.
NECTables.com is an independent reference and is not affiliated with, endorsed by, or a substitute for the National Fire Protection Association (NFPA). NEC® and National Electrical Code® are registered trademarks of the NFPA. Values shown are commonly published engineering data and independent calculations based on the methods of NFPA 70; they are not a reproduction of the Code. Always confirm against the edition adopted in your jurisdiction, including local amendments, and consult a licensed electrician or engineer before doing electrical work.