How many #12 THHN fit in 1-1/4" Flex?
3812 AWG THHN/THWN-2 wires in 1-1/4" Flexible metal conduit (FMC, Greenfield)
1.277 sq in × 40 % = 0.5108 sq in allowed. ÷ 0.0133 sq in per wire = 38.41, so 38.
This pull in numbers
- 38 wires fill
- 39.6 % of 1-1/4" Flex
- Limit for three or more
- 40 %
- For 39 or more
- 1-1/2" Flex, up to 56
- Pipe to wire diameter
- 9.81 to 1
- In THW insulation
- 28 fit
- In XHHW-2 insulation
- 28 fit
Before you pull 38
- The ground counts. Every wire in the pipe counts toward fill, the green or bare ground and the neutrals too. 38 is the total, not the hots.
- Derating. If all 38 were current-carrying, each would be adjusted to 40 % of its ampacity (Table 310.15(C)(1)): a #12 THHN at 30 A in the 90 °C column becomes 12 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 1-1/4" conduit
| Conduit | Inside area | Most #12 THHN |
|---|---|---|
| Electrical metallic tubing | 1.496 | 45 |
| Intermediate metal conduit | 1.647 | 49 |
| Rigid metal conduit (RMC, GRC) | 1.526 | 46 |
| Rigid PVC conduit, Schedule 40 | 1.453 | 43 |
| Rigid PVC conduit, Schedule 80 | 1.237 | 37 |
| Flexible metal conduit (FMC, Greenfield) | 1.277 | 38 |
| Liquidtight flexible metal conduit (LFMC) | 1.528 | 46 |
| Electrical nonmetallic tubing (smurf tube) | 1.453 | 43 |
#12 THHN in other Flex sizes
Other wire sizes in 1-1/4" Flex
#14: 52#12: 38#10: 24#8: 14#6: 10#4: 6#3: 5#2: 4#1: 3#1/0: 2#2/0: 1#3/0: 1#4/0: 1250 kcmil: 1300 kcmil: 1350 kcmil: 1