8 AWG Voltage Drop at 240V
This page provides detailed voltage drop analysis for 8 AWG conductors operating at 240V (single-phase). The 8 AWG copper conductor has a resistance of 0.778 ohms per 1000 feet and an ampacity of 50 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 8 AWG wire while staying within the NEC recommended voltage drop limits.
Maximum Distance for 8 AWG at 240V
The table below shows the maximum one-way distance you can run 8 AWG copper conductor at 240V 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 = 7.2V |
|---|---|---|---|
| 5A | 925 ft | 1542 ft | 7.2 V |
| 10A | 462 ft | 771 ft | 7.2 V |
| 15A | 308 ft | 514 ft | 7.2 V |
| 20A | 231 ft | 385 ft | 7.2 V |
| 25A | 185 ft | 308 ft | 7.2 V |
| 30A | 154 ft | 257 ft | 7.2 V |
| 40A | 115 ft | 192 ft | 7.2 V |
| 50A | 92 ft | 154 ft | 7.2 V |
| 60A (exceeds ampacity) | 77 ft | 128 ft | 7.2 V |
Voltage Drop Table — 8 AWG Copper at 240V
Complete voltage drop matrix for 8 AWG copper conductor at 240V. 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 0.778 ohms per 1000 feet.
| Distance | 5A | 10A | 15A | 20A | 25A | 30A | 40A | 50A | 60A |
|---|---|---|---|---|---|---|---|---|---|
| 25 ft | 0.2V 0.1% | 0.4V 0.2% | 0.6V 0.2% | 0.8V 0.3% | 1.0V 0.4% | 1.2V 0.5% | 1.6V 0.7% | 1.9V 0.8% | 2.3V 1.0% |
| 50 ft | 0.4V 0.2% | 0.8V 0.3% | 1.2V 0.5% | 1.6V 0.7% | 1.9V 0.8% | 2.3V 1.0% | 3.1V 1.3% | 3.9V 1.6% | 4.7V 1.9% |
| 75 ft | 0.6V 0.2% | 1.2V 0.5% | 1.8V 0.7% | 2.3V 1.0% | 2.9V 1.2% | 3.5V 1.5% | 4.7V 1.9% | 5.8V 2.4% | 7.0V 2.9% |
| 100 ft | 0.8V 0.3% | 1.6V 0.7% | 2.3V 1.0% | 3.1V 1.3% | 3.9V 1.6% | 4.7V 1.9% | 6.2V 2.6% | 7.8V 3.2% | 9.3V 3.9% |
| 125 ft | 1.0V 0.4% | 1.9V 0.8% | 2.9V 1.2% | 3.9V 1.6% | 4.9V 2.0% | 5.8V 2.4% | 7.8V 3.2% | 9.7V 4.0% | 11.7V 4.9% |
| 150 ft | 1.2V 0.5% | 2.3V 1.0% | 3.5V 1.5% | 4.7V 1.9% | 5.8V 2.4% | 7.0V 2.9% | 9.3V 3.9% | 11.7V 4.9% | 14.0V 5.8% |
| 200 ft | 1.6V 0.7% | 3.1V 1.3% | 4.7V 1.9% | 6.2V 2.6% | 7.8V 3.2% | 9.3V 3.9% | 12.4V 5.2% | 15.6V 6.5% | 18.7V 7.8% |
| 250 ft | 1.9V 0.8% | 3.9V 1.6% | 5.8V 2.4% | 7.8V 3.2% | 9.7V 4.0% | 11.7V 4.9% | 15.6V 6.5% | 19.4V 8.1% | 23.3V 9.7% |
| 300 ft | 2.3V 1.0% | 4.7V 1.9% | 7.0V 2.9% | 9.3V 3.9% | 11.7V 4.9% | 14.0V 5.8% | 18.7V 7.8% | 23.3V 9.7% | 28.0V 11.7% |
| 400 ft | 3.1V 1.3% | 6.2V 2.6% | 9.3V 3.9% | 12.4V 5.2% | 15.6V 6.5% | 18.7V 7.8% | 24.9V 10.4% | 31.1V 13.0% | 37.3V 15.6% |
| 500 ft | 3.9V 1.6% | 7.8V 3.2% | 11.7V 4.9% | 15.6V 6.5% | 19.4V 8.1% | 23.3V 9.7% | 31.1V 13.0% | 38.9V 16.2% | 46.7V 19.4% |
When to Use 8 AWG at 240V
8 AWG wire at 240V is appropriate for circuits where the amperage does not exceed 50 amps (copper, 75 degrees C) and the voltage drop at the planned distance stays within NEC recommendations. At short distances under 115 feet, 8 AWG handles 40-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 8 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, 8 AWG has an ampacity of 40 amps at 75 degrees C and a resistance of 1.28 ohms per 1000 feet. The higher resistance means aluminum requires approximately 65% 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 240V
Compare voltage drop performance across different wire gauges at 240V. Larger gauges have lower resistance and can run longer distances with less voltage drop.
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