12 AWG Voltage Drop at 120V
This page provides detailed voltage drop analysis for 12 AWG conductors operating at 120V (single-phase). The 12 AWG copper conductor has a resistance of 1.98 ohms per 1000 feet and an ampacity of 25 amps at 75 degrees C per NEC Table 310.16. Use the tables below to determine the voltage drop at any distance and amperage combination, or to find the maximum distance you can run 12 AWG wire while staying within the NEC recommended voltage drop limits.
Maximum Distance for 12 AWG at 120V
The table below shows the maximum one-way distance you can run 12 AWG copper conductor at 120V for each amperage level while maintaining voltage drop at or below 3% (branch circuit) and 5% (feeder + branch combined). If your planned run exceeds these distances, you must use a larger wire gauge. These values assume single-phase power with a 2 multiplier in the voltage drop formula.
| Amperage | Max Distance (3%) | Max Distance (5%) | 3% Drop = 3.6V |
|---|---|---|---|
| 5A | 181 ft | 303 ft | 3.6 V |
| 10A | 90 ft | 151 ft | 3.6 V |
| 15A | 60 ft | 101 ft | 3.6 V |
| 20A | 45 ft | 75 ft | 3.6 V |
| 25A | 36 ft | 60 ft | 3.6 V |
| 30A (exceeds ampacity) | 30 ft | 50 ft | 3.6 V |
Voltage Drop Table — 12 AWG Copper at 120V
Complete voltage drop matrix for 12 AWG copper conductor at 120V. Each cell shows the voltage drop in volts and percentage. Cells in red exceed the 3% NEC recommendation for branch circuits. Cells within the green range are NEC compliant. This table uses the single-phase voltage drop formula with a conductor resistance of 1.98 ohms per 1000 feet.
| Distance | 5A | 10A | 15A | 20A | 25A | 30A |
|---|---|---|---|---|---|---|
| 25 ft | 0.5V 0.4% | 1.0V 0.8% | 1.5V 1.2% | 2.0V 1.6% | 2.5V 2.1% | 3.0V 2.5% |
| 50 ft | 1.0V 0.8% | 2.0V 1.6% | 3.0V 2.5% | 4.0V 3.3% | 5.0V 4.1% | 5.9V 5.0% |
| 75 ft | 1.5V 1.2% | 3.0V 2.5% | 4.5V 3.7% | 5.9V 5.0% | 7.4V 6.2% | 8.9V 7.4% |
| 100 ft | 2.0V 1.6% | 4.0V 3.3% | 5.9V 5.0% | 7.9V 6.6% | 9.9V 8.3% | 11.9V 9.9% |
| 125 ft | 2.5V 2.1% | 5.0V 4.1% | 7.4V 6.2% | 9.9V 8.3% | 12.4V 10.3% | 14.8V 12.4% |
| 150 ft | 3.0V 2.5% | 5.9V 5.0% | 8.9V 7.4% | 11.9V 9.9% | 14.8V 12.4% | 17.8V 14.8% |
| 200 ft | 4.0V 3.3% | 7.9V 6.6% | 11.9V 9.9% | 15.8V 13.2% | 19.8V 16.5% | 23.8V 19.8% |
| 250 ft | 5.0V 4.1% | 9.9V 8.3% | 14.8V 12.4% | 19.8V 16.5% | 24.8V 20.6% | 29.7V 24.8% |
| 300 ft | 5.9V 5.0% | 11.9V 9.9% | 17.8V 14.8% | 23.8V 19.8% | 29.7V 24.8% | 35.6V 29.7% |
| 400 ft | 7.9V 6.6% | 15.8V 13.2% | 23.8V 19.8% | 31.7V 26.4% | 39.6V 33.0% | 47.5V 39.6% |
| 500 ft | 9.9V 8.3% | 19.8V 16.5% | 29.7V 24.8% | 39.6V 33.0% | 49.5V 41.3% | 59.4V 49.5% |
When to Use 12 AWG at 120V
12 AWG wire at 120V is appropriate for circuits where the amperage does not exceed 25 amps (copper, 75 degrees C) and the voltage drop at the planned distance stays within NEC recommendations. At short distances under 45 feet, 12 AWG handles 20-amp loads with comfortable voltage drop margin. As the distance increases, the voltage drop grows proportionally, and at some point a larger gauge becomes necessary.
If 12 AWG does not provide adequate voltage drop performance for your run distance, consider the next larger gauge. Each step up in wire size roughly doubles the maximum distance for the same voltage drop percentage. Alternatively, if the circuit operates at 120 volts and the distance is problematic, consider whether the load can be served by a 240-volt circuit instead, which halves the percentage voltage drop and doubles the effective run distance for the same wire gauge.
For aluminum conductors, 12 AWG has an ampacity of 20 amps at 75 degrees C and a resistance of 3.25 ohms per 1000 feet. The higher resistance means aluminum requires approximately 64% more distance correction compared to copper, often requiring an increase of one or two gauge sizes to match copper's voltage drop performance at the same distance.
Related Wire Sizes at 120V
Compare voltage drop performance across different wire gauges at 120V. Larger gauges have lower resistance and can run longer distances with less voltage drop.
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