3-1/2" Flex conduit fill
3-1/2" Flexible metal conduit (FMC, Greenfield) has an inside area of 9.621 sq in (3.500 in across). Three or more wires may take 40 % of it: 3.8484 sq in.
- One wire, 53 %
- 5.0991 sq in
- Two wires, 31 %
- 2.9825 sq in
- Three or more, 40 %
- 3.8484 sq in
- Nipple, 60 %
- 5.7726 sq in
- Support
- Every 4.5 ft, 12 in from boxes
How many wires fit in 3-1/2" Flex
All wires the same size and type, by Annex C's method. For a mix of sizes, open the calculator.
| Wire size | THHN/THWN-2 | XHHW-2 | THW/THW-2 |
|---|---|---|---|
| 14 AWG | 396 | 277 | 277 |
| 12 AWG | 289 | 212 | 212 |
| 10 AWG | 182 | 158 | 158 |
| 8 AWG | 105 | 88 | 88 |
| 6 AWG | 76 | 65 | 53 |
| 4 AWG | 46 | 47 | 39 |
| 3 AWG | 39 | 40 | 34 |
| 2 AWG | 33 | 33 | 29 |
| 1 AWG | 24 | 25 | 20 |
| 1/0 AWG | 20 | 21 | 17 |
| 2/0 AWG | 17 | 17 | 14 |
| 3/0 AWG | 14 | 14 | 12 |
| 4/0 AWG | 12 | 12 | 10 |
| 250 kcmil | 9 | 10 | 8 |
| 300 kcmil | 8 | 8 | 7 |
| 350 kcmil | 7 | 7 | 6 |
| 400 kcmil | 6 | 6 | 6 |
| 500 kcmil | 5 | 5 | 5 |
| 600 kcmil | 4 | 4 | 4 |
| 700 kcmil | 4 | 4 | 3 |
| 750 kcmil | 3 | 3 | 3 |
| 800 kcmil | 3 | 3 | 3 |
| 900 kcmil | 3 | 3 | 3 |
| 1000 kcmil | 3 | 3 | 2 |
Other 3-1/2" conduit
| Conduit | Inside area | #14 | #12 | #10 | #8 | #6 |
|---|---|---|---|---|---|---|
| Flexible metal conduit (FMC, Greenfield) | 9.621 | 396 | 289 | 182 | 105 | 76 |
| Electrical metallic tubing | 11.545 | 476 | 347 | 219 | 126 | 91 |
| Intermediate metal conduit | 10.584 | 436 | 318 | 200 | 115 | 83 |
| Rigid metal conduit (RMC, GRC) | 10.010 | 412 | 301 | 189 | 109 | 79 |
| Rigid PVC conduit, Schedule 40 | 9.737 | 401 | 293 | 184 | 106 | 77 |
| Rigid PVC conduit, Schedule 80 | 8.688 | 358 | 261 | 164 | 95 | 68 |
| Liquidtight flexible metal conduit (LFMC) | 9.731 | 401 | 292 | 184 | 106 | 76 |
About Flex
Flex is supported every 4-1/2 ft and within 12 in of each box (348.30). Short whips to equipment have their own exceptions. See strap spacing and the fill rules.