Voltage drop tables for common wire sizes at various run lengths. Long wire runs increase voltage drop — use these charts to verify your wire gauge is adequate for the distance, or use our wire size calculator for custom scenarios.
The table below shows voltage drop for the most common gauge-and-distance combinations at 120V (copper, single-phase). Runs that exceed the 3% NEC recommendation are flagged.
| Wire & Distance | Load | Voltage Drop | Status | Detail |
|---|---|---|---|---|
| 12 AWG @ 50 ft | 20A / 120V | 3.2% | Borderline | Full chart → |
| 14 AWG @ 50 ft | 15A / 120V | 4.0% | Over 3% | Full chart → |
| 10 AWG @ 100 ft | 30A / 240V | 3.1% | Borderline | Full chart → |
| 6 AWG @ 100 ft | 50A / 240V | 2.6% | OK | Full chart → |
| 8 AWG @ 75 ft | 40A / 240V | 2.1% | OK | Full chart → |
| 4 AWG @ 150 ft | 60A / 240V | 3.0% | Borderline | Full chart → |
Every foot of wire adds resistance. For long runs, the cumulative voltage drop can exceed safe limits even if the wire's ampacity rating is sufficient. NEC recommends keeping voltage drop under 3% for branch circuits.
As a rule of thumb: doubling the distance doubles the voltage drop. To compensate, move up one or two wire sizes: each AWG step cuts voltage drop by about 21%, so going from 12 AWG to 10 AWG reduces it by roughly 37%.
Every foot of wire adds resistance, which causes voltage drop. The longer the run, the more voltage is lost before it reaches the load. For long distances you often need to upsize the wire gauge beyond what the ampacity alone requires, so that the total voltage drop stays within acceptable limits (typically 3% for branch circuits per NEC recommendation).
The NEC recommends a maximum 3% voltage drop for branch circuits and 5% total for the combination of feeder and branch circuit. For example, on a 120V circuit 3% is 3.6V, meaning the voltage at the load should be at least 116.4V. On a 240V circuit 3% is 7.2V. These are recommendations, not hard code requirements, but exceeding them can cause equipment malfunction, dim lighting, and motor overheating.
Usually, yes. Doubling the distance doubles the voltage drop, so a wire gauge that works fine at 25 feet may exceed the 3% limit at 50 or 75 feet. As a rule of thumb, going up one AWG size (e.g., from 12 AWG to 10 AWG) reduces voltage drop by about 37%. Use a voltage drop calculator or the charts on this page to check whether your planned wire gauge is adequate for the run length.