How many #12 THHN fit in 3/8" Flex?
312 AWG THHN/THWN-2 wires in 3/8" Flexible metal conduit (FMC, Greenfield)
0.116 sq in × 40 % = 0.0464 sq in allowed. ÷ 0.0133 sq in per wire = 3.49, so 3.
This pull in numbers
- 3 wires fill
- 34.4 % of 3/8" Flex
- Limit for three or more
- 40 %
- For 4 or more
- 1/2" Flex, up to 9
- Pipe to wire diameter
- 2.95 to 1
- In THW insulation
- 1 fit
- In XHHW-2 insulation
- 1 fit
The pipe is 2.95 times the wire's diameter, inside the 2.8 to 3.2 range where three wires can wedge side by side on a pull. If you pull exactly three, go up a size or pull with care.
Before you pull 3
- The ground counts. Every wire in the pipe counts toward fill, the green or bare ground and the neutrals too. 3 is the total, not the hots.
- Bends. A full pipe pulls hard. Keep to 360° of bends between pull points, less for a tight fill.
#12 THHN in other 3/8" conduit
| Conduit | Inside area | Most #12 THHN |
|---|---|---|
| Flexible metal conduit (FMC, Greenfield) | 0.116 | 3 |
| Liquidtight flexible metal conduit (LFMC) | 0.192 | 5 |