Voltage Drop Calculator

Quickly compute the voltage drop for your electrical circuits with our Voltage Drop Calculator, designed specifically for electrical contractors and engineers. Input the voltage, phase, current, conductor material, wire size, and distance, and the calculator will provide you with the voltage drop, voltage at load, and the percentage drop. Follow the easy steps below and get a clear view of your circuit’s performance and potential issues!

Voltage drop calculator


Step 1: Input the voltage, phases, amperes, conductor material, wire size, and distance in the corresponding input fields.
Step 2: Choose your preferred unit for distance (feet or meters).

Step 3: Click Calculate to compute the voltage drop, voltage at load, and the percentage drop.

Step 4: Review the results and gain valuable insights into your circuit’s performance. This can help you plan more effectively as an electrical contractor or engineer.

Voltage Drop Calculator
Wire Size
Voltage Drop
Voltage at Load
Percentage Drop

Key Terms

Source Voltage - Enter the circuit's source voltage. Common voltages for single-phase circuits are usually 115V or 120V, while three-phase circuits are typically 208V, 230V, or 480V.

Amperage - Specify the maximum current in amps that the circuit will handle. If dealing with motors, consider multiplying the nameplate Full Load Amps (FLA) by 1.25 for appropriate wire sizing.

Phases - Indicate the phase count in the circuit, typically either single-phase or three-phase. Single-phase circuits require three wires, while three-phase circuits need four, including a ground wire.

Conductor - Choose the type of conductor material in your wire. The most typical choices are copper and aluminum.

Wire Size - Select the wire size in your circuit. It is typically measured in AWG or kcmil.

Distance - Input the one-way distance the wires in your circuit travel, usually measured in feet.

Note: The results of this calculator are based on conductor temperatures being at 75°C. Always consider the total length of the circuit for calculations, and if your project requires more intricate calculations, it's recommended to consult with an engineer.

Reference: NFPA 70, National Electrical Code, Table 310.15(B)(16-17)