3-1/2" Rigid conduit fill
3-1/2" Rigid metal conduit (RMC, GRC) has an inside area of 10.010 sq in (3.570 in across). Three or more wires may take 40 % of it: 4.0040 sq in.
- One wire, 53 %
- 5.3053 sq in
- Two wires, 31 %
- 3.1031 sq in
- Three or more, 40 %
- 4.0040 sq in
- Nipple, 60 %
- 6.0060 sq in
- Support
- Every 10 ft, 3 ft from boxes
- Sold in
- 10 ft sticks
How many wires fit in 3-1/2" Rigid
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 | 412 | 288 | 288 |
| 12 AWG | 301 | 221 | 221 |
| 10 AWG | 189 | 164 | 164 |
| 8 AWG | 109 | 91 | 91 |
| 6 AWG | 79 | 68 | 55 |
| 4 AWG | 48 | 49 | 41 |
| 3 AWG | 41 | 41 | 35 |
| 2 AWG | 34 | 35 | 30 |
| 1 AWG | 25 | 26 | 21 |
| 1/0 AWG | 21 | 22 | 18 |
| 2/0 AWG | 18 | 18 | 15 |
| 3/0 AWG | 15 | 15 | 13 |
| 4/0 AWG | 12 | 12 | 10 |
| 250 kcmil | 10 | 10 | 8 |
| 300 kcmil | 8 | 9 | 7 |
| 350 kcmil | 7 | 7 | 6 |
| 400 kcmil | 7 | 7 | 6 |
| 500 kcmil | 5 | 5 | 5 |
| 600 kcmil | 4 | 4 | 4 |
| 700 kcmil | 4 | 4 | 3 |
| 750 kcmil | 4 | 4 | 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 |
|---|---|---|---|---|---|---|
| Rigid metal conduit (RMC, GRC) | 10.010 | 412 | 301 | 189 | 109 | 79 |
| Electrical metallic tubing | 11.545 | 476 | 347 | 219 | 126 | 91 |
| Intermediate metal conduit | 10.584 | 436 | 318 | 200 | 115 | 83 |
| Rigid PVC conduit, Schedule 40 | 9.737 | 401 | 293 | 184 | 106 | 77 |
| Rigid PVC conduit, Schedule 80 | 8.688 | 358 | 261 | 164 | 95 | 68 |
| Flexible metal conduit (FMC, Greenfield) | 9.621 | 396 | 289 | 182 | 105 | 76 |
| Liquidtight flexible metal conduit (LFMC) | 9.731 | 401 | 292 | 184 | 106 | 76 |
About Rigid
Rigid (galvanized rigid conduit, GRC) has the thickest wall and the least room inside of the steel types. Support follows 344.30: within 3 ft of each box, then every 10 ft, or longer on straight runs with threaded couplings (Table 344.30(B)(2)). See strap spacing and the fill rules.