How many #8 THHN fit in 1/2" IMC?
38 AWG THHN/THWN-2 wires in 1/2" Intermediate metal conduit
0.342 sq in × 40 % = 0.1368 sq in allowed. ÷ 0.0366 sq in per wire = 3.74, so 3.
This pull in numbers
- 3 wires fill
- 32.1 % of 1/2" IMC
- Limit for three or more
- 40 %
- For 4 or more
- 3/4" IMC, up to 6
- Pipe to wire diameter
- 3.06 to 1
- In THW insulation
- 3 fit
- In XHHW-2 insulation
- 3 fit
The pipe is 3.06 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.
#8 THHN in other 1/2" conduit
| Conduit | Inside area | Most #8 THHN |
|---|---|---|
| Electrical metallic tubing | 0.304 | 3 |
| Intermediate metal conduit | 0.342 | 3 |
| Rigid metal conduit (RMC, GRC) | 0.314 | 3 |
| Rigid PVC conduit, Schedule 40 | 0.285 | 3 |
| Rigid PVC conduit, Schedule 80 | 0.217 | 1 |
| Flexible metal conduit (FMC, Greenfield) | 0.317 | 3 |
| Liquidtight flexible metal conduit (LFMC) | 0.314 | 3 |
| Electrical nonmetallic tubing (smurf tube) | 0.285 | 3 |