8 AWG Voltage Drop Chart
8 AWG copper wire has a resistance of 0.778 ohms per 1000 feet. NEC 240.4(D) and the standard ampacity tables cap this gauge at 50A for a branch-circuit breaker (60°C ampacity: 40A; 75°C: 50A). At 100 feet on a 120V circuit, it stays under 3% voltage drop up to about 23A.
8 AWG Wire Specifications
| Property | Value |
|---|---|
| Gauge | 8 AWG |
| Resistance (copper) | 0.778 Ω per 1000ft |
| Ampacity (60°C) | 40A |
| Ampacity (75°C) | 50A |
| NEC branch-circuit OCP | 50A |
| Amps that land on 3% drop at 100ft (120V) | ~23A |
Voltage Drop by Amps & Distance (120V)
| Amps | 50ft | 100ft | 150ft | 200ft |
|---|---|---|---|---|
| 10A | 0.6483% | 1.3% | 1.95% | 2.59% |
| 15A | 0.9725% | 1.95% | 2.92% | 3.89% |
| 20A | 1.3% | 2.59% | 3.89% | 5.19% |
| 25A | 1.62% | 3.24% | 4.86% | 6.48% |
| 30A | 1.95% | 3.89% | 5.84% | 7.78% |
| 40A | 2.59% | 5.19% | 7.78% | 10.37% |
| 50A | 3.24% | 6.48% | 9.73% | 12.97% |
| 60A | 3.89% | 7.78% | 11.67% | 15.56% |
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 8 AWG
Typical applications: Large appliance circuits: dryers, ranges, HVAC, sub-panels at shorter distances.
Under typical 75°C-termination assumptions, 8 AWG is commonly protected by up to 50A 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.