Voltage Drop Calculator

Use it when your task matches one of these common needs: Estimate voltage drop for a branch circuit run. Compare common copper AWG wire sizes. It works best when you already know the measurements, amounts, units, or options the page asks for.

In plain language: The calculator multiplies current by conductor resistance and one-way length. Single-phase/DC uses a 2x path factor; three-phase uses the square root of 3. The examples on the page are there so you can compare your inputs with a worked example before copying the answer.

Source voltage: the voltage at the supply side before the wire run loses voltage. Current amps: the load current flowing through the conductor. One-way length: the distance from source to load. The calculator applies the circuit-path factor for the selected phase. Copper wire size: the AWG size used to look up approximate copper resistance.

Read the headline answer, then check the supporting lines and examples to understand how the calculator got there. If one input changes, rerun the tool and compare the new answer instead of guessing.

This is a simplified planning estimate. Real electrical work needs code checks, conductor temperature, material, installation method, and a qualified professional. Also check the unit, scale, mode, and result limit because small input changes can change the answer.

A simple single-phase or DC run uses an out-and-back path, so the length factor is 2. A balanced three-phase estimate uses the square root of 3. Real installations can need more detailed impedance and code checks.

No. The calculator runs in your browser tab. Your recent answers stay only on the page while you use it, and they are not sent to a server.