How Many 1/0 AWG Wires Fit in RMC Conduit?
Complete NEC-compliant fill chart for 1/0 AWG THHN wires in Rigid Metal Conduit (RMC) conduit. Maximum wire counts for all standard conduit sizes.
Quick Answer
For 1/0 AWG THHN wires in RMC conduit at 40% fill (3+ wires):
- • 3/4" RMC: 1 wires
- • 1" RMC: 1 wires
- • 1-1/4" RMC: 3 wires
1/0 AWG in RMC Conduit Fill Chart
| Conduit Size | Max Wires (40% Fill) | Fill % | Max Wires (Nipple 60%) | Fill % |
|---|---|---|---|---|
| 3/4" | 1 | 34% | 1 | 34% |
| 1" | 1 | 21% | 2 | 42% |
| 1-1/4" | 3 | 36% | 4 | 49% |
| 1-1/2" | 4 | 36% | 6 | 54% |
| 2" | 7 | 38% | 11 | 60% |
| 2-1/2" | 12 | 37% | 19 | 59% |
| 3" | 19 | 39% | 28 | 58% |
| 3-1/2" | 25 | 40% | 37 | 59% |
| 4" | 32 | 40% | 48 | 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 1/0 AWG THHN conductors that can fit in each RMC conduit size while maintaining NEC compliance.
Calculation Example
Question: How many 1/0 AWG THHN wires can fit in 1" RMC conduit?
Wire area: 0.1855 sq in per conductor
Conduit internal area: 0.887 sq in
Allowable fill (40%): 0.3548 sq in
Maximum wires: 0.3548 ÷ 0.1855 = 1 wires
Answer: You can fit up to 1 wires of 1/0 AWG THHN in 1" RMC conduit.