How many #12 THHN fit in 1" Flex?
2412 AWG THHN/THWN-2 wires in 1" Flexible metal conduit (FMC, Greenfield)
0.817 sq in × 40 % = 0.3268 sq in allowed. ÷ 0.0133 sq in per wire = 24.57, so 24.
This pull in numbers
- 24 wires fill
- 39.1 % of 1" Flex
- Limit for three or more
- 40 %
- For 25 or more
- 1-1/4" Flex, up to 38
- Pipe to wire diameter
- 7.85 to 1
- In THW insulation
- 18 fit
- In XHHW-2 insulation
- 18 fit
Before you pull 24
- The ground counts. Every wire in the pipe counts toward fill, the green or bare ground and the neutrals too. 24 is the total, not the hots.
- Derating. If all 24 were current-carrying, each would be adjusted to 45 % of its ampacity (Table 310.15(C)(1)): a #12 THHN at 30 A in the 90 °C column becomes 13.5 A. Grounds don't count as current-carrying. How derating works
- Bends. A full pipe pulls hard. Keep to 360° of bends between pull points, less for a tight fill.
#12 THHN in other 1" conduit
| Conduit | Inside area | Most #12 THHN |
|---|---|---|
| Electrical metallic tubing | 0.864 | 26 |
| Intermediate metal conduit | 0.959 | 29 |
| Rigid metal conduit (RMC, GRC) | 0.887 | 26 |
| Rigid PVC conduit, Schedule 40 | 0.832 | 25 |
| Rigid PVC conduit, Schedule 80 | 0.688 | 20 |
| Flexible metal conduit (FMC, Greenfield) | 0.817 | 24 |
| Liquidtight flexible metal conduit (LFMC) | 0.873 | 26 |
| Electrical nonmetallic tubing (smurf tube) | 0.832 | 25 |