How Many 8 AWG Wires Fit in RMC Conduit?
Complete NEC-compliant fill chart for 8 AWG THHN wires in Rigid Metal Conduit (RMC) conduit. Maximum wire counts for all standard conduit sizes.
Quick Answer
For 8 AWG THHN wires in RMC conduit at 40% fill (3+ wires):
- • 1/2" RMC: 3 wires
- • 3/4" RMC: 6 wires
- • 1" RMC: 9 wires
8 AWG in RMC Conduit Fill Chart
| Conduit Size | Max Wires (40% Fill) | Fill % | Max Wires (Nipple 60%) | Fill % |
|---|---|---|---|---|
| 1/2" | 3 | 35% | 5 | 58% |
| 3/4" | 6 | 40% | 9 | 60% |
| 1" | 9 | 37% | 14 | 58% |
| 1-1/4" | 16 | 38% | 25 | 60% |
| 1-1/2" | 22 | 39% | 33 | 58% |
| 2" | 37 | 40% | 55 | 59% |
| 2-1/2" | 65 | 40% | 98 | 60% |
| 3" | 97 | 40% | 146 | 60% |
| 3-1/2" | 127 | 40% | 191 | 60% |
| 4" | 162 | 40% | 244 | 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 8 AWG THHN conductors that can fit in each RMC conduit size while maintaining NEC compliance.
Calculation Example
Question: How many 8 AWG THHN wires can fit in 3/4" RMC conduit?
Wire area: 0.0366 sq in per conductor
Conduit internal area: 0.549 sq in
Allowable fill (40%): 0.2196 sq in
Maximum wires: 0.2196 ÷ 0.0366 = 6 wires
Answer: You can fit up to 6 wires of 8 AWG THHN in 3/4" RMC conduit.