Voltage Drop Calculator

This calculator estimates expected voltage loss on a feeder or branch circuit and reports it in volts and percent.

It is useful during early panel design, motor feeder checks, lighting runs, and remote load planning before installation details are finalized.

Current is the operating load current, while length should be entered as the one-way distance between source and load.

Cable section represents conductor area, nominal voltage defines the system base, and material selects the copper or aluminum resistivity assumption.

For single-phase circuits, the conductor path is doubled to represent the outgoing and return path; for three-phase circuits, the square-root-of-three factor is used for balanced line calculation.

The tool uses a simplified resistance-based voltage-drop model and does not separately model reactance, temperature correction, harmonics, or power-factor effects.

The voltage result is the approximate loss at the load end, and the percentage result expresses that loss against nominal system voltage.

If the percentage is high, evaluate a larger cable section, shorter route, lower load current, or a different supply arrangement with the project team.

A 32 A load, 60 m copper run, 6 mm2 section, and 400 V three-phase supply is a realistic first-pass check for a remote motor feeder.

When the output is close to the accepted limit, also review starting current, protection coordination, ampacity, installation method, and ambient temperature.

This content is informational and is not a complete electrical design, installation instruction, inspection approval, or safety certification.

Before working on live or permanent electrical systems, validate against local codes, IEC/NEC requirements where applicable, manufacturer data, and a licensed electrical engineer or qualified electrician.