How Many 12 AWG Wires Fit in RMC Conduit?
Complete NEC-compliant fill chart for 12 AWG THHN wires in Rigid Metal Conduit (RMC) conduit. Maximum wire counts for all standard conduit sizes.
Quick Answer
For 12 AWG THHN wires in RMC conduit at 40% fill (3+ wires):
- • 1/2" RMC: 9 wires
- • 3/4" RMC: 16 wires
- • 1" RMC: 26 wires
12 AWG in RMC Conduit Fill Chart
| Conduit Size | Max Wires (40% Fill) | Fill % | Max Wires (Nipple 60%) | Fill % |
|---|---|---|---|---|
| 1/2" | 9 | 38% | 14 | 59% |
| 3/4" | 16 | 39% | 24 | 58% |
| 1" | 26 | 39% | 40 | 60% |
| 1-1/4" | 45 | 39% | 68 | 59% |
| 1-1/2" | 62 | 40% | 93 | 60% |
| 2" | 102 | 40% | 153 | 60% |
| 2-1/2" | 180 | 40% | 271 | 60% |
| 3" | 268 | 40% | 402 | 60% |
| 3-1/2" | 350 | 40% | 526 | 60% |
| 4" | 448 | 40% | 672 | 60% |
Understanding the Fill Chart
According to NEC (National Electrical Code) Chapter 9, Table 1, the maximum conduit fill percentage depends on the number of conductors:
- 1 conductor: 53% fill maximum
- 2 conductors: 31% fill maximum
- 3 or more conductors: 40% fill maximum
- Nipples (24" or less): 60% fill maximum
This chart shows the maximum number of 12 AWG THHN conductors that can fit in each RMC conduit size while maintaining NEC compliance.
Calculation Example
Question: How many 12 AWG THHN wires can fit in 3/4" RMC conduit?
Wire area: 0.0133 sq in per conductor
Conduit internal area: 0.549 sq in
Allowable fill (40%): 0.2196 sq in
Maximum wires: 0.2196 ÷ 0.0133 = 16 wires
Answer: You can fit up to 16 wires of 12 AWG THHN in 3/4" RMC conduit.