How Many 4 AWG Wires Fit in RMC Conduit?
Complete NEC-compliant fill chart for 4 AWG THHN wires in Rigid Metal Conduit (RMC) conduit. Maximum wire counts for all standard conduit sizes.
Quick Answer
For 4 AWG THHN wires in RMC conduit at 40% fill (3+ wires):
- • 1/2" RMC: 1 wires
- • 3/4" RMC: 2 wires
- • 1" RMC: 4 wires
4 AWG in RMC Conduit Fill Chart
| Conduit Size | Max Wires (40% Fill) | Fill % | Max Wires (Nipple 60%) | Fill % |
|---|---|---|---|---|
| 1/2" | 1 | 26% | 2 | 52% |
| 3/4" | 2 | 30% | 3 | 45% |
| 1" | 4 | 37% | 6 | 56% |
| 1-1/4" | 7 | 38% | 11 | 59% |
| 1-1/2" | 10 | 40% | 15 | 60% |
| 2" | 16 | 39% | 24 | 58% |
| 2-1/2" | 29 | 40% | 43 | 59% |
| 3" | 43 | 40% | 64 | 59% |
| 3-1/2" | 56 | 40% | 84 | 59% |
| 4" | 72 | 40% | 108 | 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 4 AWG THHN conductors that can fit in each RMC conduit size while maintaining NEC compliance.
Calculation Example
Question: How many 4 AWG THHN wires can fit in 3/4" RMC conduit?
Wire area: 0.0824 sq in per conductor
Conduit internal area: 0.549 sq in
Allowable fill (40%): 0.2196 sq in
Maximum wires: 0.2196 ÷ 0.0824 = 2 wires
Answer: You can fit up to 2 wires of 4 AWG THHN in 3/4" RMC conduit.