Voltage Drop Calculator 2026
Instantly calculate voltage loss, wire efficiency, and load voltage for single-phase and three-phase electrical circuits. Fully compliant with NEC wire sizing standards.
Circuit Parameters
Define your electrical load and wire specifications
Select the type of electrical system
Material resistivity constant at 75°C
Maximum expected current flowing through the wire
Nominal voltage at the power source
Distance from the power source to the load
American Wire Gauge size of the conductor
Circuit Analysis
Voltage loss & efficiency metrics
Enter your circuit parameters above and click Calculate Voltage Drop to reveal the voltage loss, load voltage, and NEC compliance status.
AWG Wire Sizes & Circular Mils
Standard American Wire Gauge (AWG) sizes, their cross-sectional area in Circular Mils (CM), and approximate metric area.
| AWG Size | Circular Mils (CM) | Area (mm²) |
|---|---|---|
| 14 AWG | 4,110 | 2.08 |
| 12 AWG | 6,530 | 3.31 |
| 10 AWG | 10,380 | 5.26 |
| 8 AWG | 16,510 | 8.37 |
| 6 AWG | 26,240 | 13.30 |
| 4 AWG | 41,740 | 21.15 |
| 3 AWG | 52,620 | 26.67 |
| 2 AWG | 66,360 | 33.62 |
| 1 AWG | 83,690 | 42.41 |
| 1/0 AWG | 105,600 | 53.50 |
| 2/0 AWG | 133,100 | 67.43 |
| 3/0 AWG | 167,800 | 85.02 |
| 4/0 AWG | 211,600 | 107.22 |
Voltage Drop & Wiring FAQ
Learn more about electrical resistance, NEC standards, and how to optimize your circuit wiring.
Voltage drop is the reduction in electrical potential (voltage) along the path of a current flowing in an electrical circuit. It occurs due to the resistance or impedance of the wire conductors. Excessive voltage drop can cause equipment to operate poorly, overheat, or fail.
Voltage drop is calculated using the formula: VD = (2 * K * I * L) / CM for single-phase circuits, and VD = (1.732 * K * I * L) / CM for three-phase circuits. Here, K is the specific resistivity of the wire material, I is the current in amps, L is the one-way length in feet, and CM is the circular mil area of the wire.
The National Electrical Code (NEC) recommends a maximum total voltage drop of 5% for the combined feeder and branch circuit. For branch circuits alone, the recommended maximum voltage drop is 3% to ensure maximum efficiency and proper equipment operation.
Different materials have different electrical resistivities (represented by ‘K’ in the formula). Copper has a lower resistivity (K ≈ 12.9) compared to aluminum (K ≈ 21.2). Therefore, an aluminum wire will have a higher resistance and cause a greater voltage drop than a copper wire of the exact same size and length.
Voltage drop is directly proportional to the length of the wire; doubling the length doubles the voltage drop. Conversely, it is inversely proportional to the cross-sectional area (Circular Mils) of the wire; using a thicker wire (lower AWG number) reduces the resistance and minimizes the voltage drop.