4 AWG Voltage Drop Chart
4 AWG copper wire has a resistance of 0.308 ohms per 1000 feet. NEC 240.4(D) and the standard ampacity tables cap this gauge at 85A for a branch-circuit breaker (60°C ampacity: 70A; 75°C: 85A). At 100 feet on a 120V circuit, it stays under 3% voltage drop up to about 58A.
4 AWG Wire Specifications
| Property | Value |
|---|---|
| Gauge | 4 AWG |
| Resistance (copper) | 0.308 Ω per 1000ft |
| Ampacity (60°C) | 70A |
| Ampacity (75°C) | 85A |
| NEC branch-circuit OCP | 85A |
| Amps that land on 3% drop at 100ft (120V) | ~58A |
Voltage Drop by Amps & Distance (120V)
| Amps | 50ft | 100ft | 150ft | 200ft |
|---|---|---|---|---|
| 10A | 0.2567% | 0.5133% | 0.77% | 1.03% |
| 15A | 0.385% | 0.77% | 1.16% | 1.54% |
| 20A | 0.5133% | 1.03% | 1.54% | 2.05% |
| 25A | 0.6417% | 1.28% | 1.93% | 2.57% |
| 30A | 0.77% | 1.54% | 2.31% | 3.08% |
| 40A | 1.03% | 2.05% | 3.08% | 4.11% |
| 50A | 1.28% | 2.57% | 3.85% | 5.13% |
| 60A | 1.54% | 3.08% | 4.62% | 6.16% |
| 80A | 2.05% | 4.11% | 6.16% | 8.21% |
| 100A | 2.57% | 5.13% | 7.7% | 10.27% |
Green = within the 3% branch-circuit drop target, Amber = 3-5% (past branch target, within 5% feeder+branch total), Red = past the 5% feeder+branch total recommendation
When to Use 4 AWG
Typical applications: Sub-panel feeders, large HVAC, EV chargers, and medium commercial loads.
Under typical 75°C-termination assumptions, 4 AWG is commonly protected by up to 85A branch-circuit OCP. Real install ceilings depend on conductor and termination temperature ratings, cable type (NM-B is limited to the 60°C column in residential use, so the usable value is lower), NEC 310.15(C)(1) bundling adjustments, and NEC 310.15(B) ambient corrections. Even with ampacity margin, longer runs may fall outside the 3% branch-circuit drop target recommended in NEC 210.19(A) Informational Note 4, which is why the distance table above matters.