Voltage Drop Calculator

Voltage Drop – Definition

Voltage drop is the reduction in electrical potential that occurs as current flows through a conductor. All cables have electrical resistance, and this resistance causes some of the supplied voltage to be lost before it reaches the load. Excessive voltage drop can lead to equipment malfunction, overheating, reduced efficiency, or failure to operate.

Background Theory

The voltage drop along a conductor is determined by Ohm’s law:

Where:

• I = current (A)

• R = resistance of the conductor (Ω)

The resistance of a cable is calculated using:

Where:

• ρ = electrical resistivity of the conductor (Ω·mm²/m)

• L = length of the cable (m)

• A = cross-sectional area (mm²)

Since current must travel to the load and back, the total conductor length is typically 2 × L.
Copper has lower resistivity than aluminum, so it experiences less voltage drop for the same current and cable size.

Voltage drop percentage is often evaluated to ensure compliance with standards (commonly 2–5%).

How This Calculator Works

This calculator estimates voltage drop by:

1. Taking inputs for supply voltage, current, cable length, cross-sectional area, and conductor material

2. Determining conductor resistivity based on copper or aluminum

3. Calculating total cable resistance

4. Applying Ohm’s law to compute the voltage drop

5. Computing the final voltage at the load

6. Displaying the voltage drop percentage

This allows fast and accurate evaluation of voltage losses in electrical wiring systems for residential, industrial, and engineering applications.