12 AWG Voltage Drop Chart
12 AWG copper wire has a resistance of 1.98 ohms per 1000 feet. NEC 240.4(D) and the standard ampacity tables cap this gauge at 20A for a branch-circuit breaker (60°C ampacity: 20A; 75°C: 25A). At 100 feet on a 120V circuit, it stays under 3% voltage drop up to about 9A.
12 AWG Wire Specifications
| Property | Value |
|---|---|
| Gauge | 12 AWG |
| Resistance (copper) | 1.98 Ω per 1000ft |
| Ampacity (60°C) | 20A |
| Ampacity (75°C) | 25A |
| NEC branch-circuit OCP | 20A (capped by NEC 240.4(D)) |
| Amps that land on 3% drop at 100ft (120V) | ~9A |
Voltage Drop by Amps & Distance (120V)
| Amps | 50ft | 100ft | 150ft | 200ft |
|---|---|---|---|---|
| 10A | 1.65% | 3.3% | 4.95% | 6.6% |
| 15A | 2.48% | 4.95% | 7.43% | 9.9% |
| 20A | 3.3% | 6.6% | 9.9% | 13.2% |
| 25A | 4.13% | 8.25% | 12.38% | 16.5% |
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 12 AWG
Typical applications: Residential branch circuits: lighting, outlets, and small appliance circuits.
Under typical 75°C-termination assumptions, 12 AWG is commonly protected by up to 20A branch-circuit OCP (NEC 240.4(D) caps it here even though the 75°C ampacity table lists 25A). 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.