How many #10 THHN fit in 1/2" Rigid?
610 AWG THHN/THWN-2 wires in 1/2" Rigid metal conduit (RMC, GRC)
0.314 sq in × 40 % = 0.1256 sq in allowed. ÷ 0.0211 sq in per wire = 5.95, which Note 7 rounds up to 6 because the decimal is 0.8 or more.
This pull in numbers
- 6 wires fill
- 40.3 % of 1/2" Rigid
- Limit for three or more
- 40 %
- For 7 or more
- 3/4" Rigid, up to 10
- Pipe to wire diameter
- 3.85 to 1
- In THW insulation
- 5 fit
- In XHHW-2 insulation
- 5 fit
Before you pull 6
- The ground counts. Every wire in the pipe counts toward fill, the green or bare ground and the neutrals too. 6 is the total, not the hots.
- Derating. If all 6 were current-carrying, each would be adjusted to 80 % of its ampacity (Table 310.15(C)(1)): a #10 THHN at 40 A in the 90 °C column becomes 32 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.
#10 THHN in other 1/2" conduit
| Conduit | Inside area | Most #10 THHN |
|---|---|---|
| Electrical metallic tubing | 0.304 | 5 |
| Intermediate metal conduit | 0.342 | 6 |
| Rigid metal conduit (RMC, GRC) | 0.314 | 6 |
| Rigid PVC conduit, Schedule 40 | 0.285 | 5 |
| Rigid PVC conduit, Schedule 80 | 0.217 | 4 |
| Flexible metal conduit (FMC, Greenfield) | 0.317 | 6 |
| Liquidtight flexible metal conduit (LFMC) | 0.314 | 6 |
| Electrical nonmetallic tubing (smurf tube) | 0.285 | 5 |