Voltage Drop (Single Phase)

Approximate copper conductor voltage drop calculation.

oltage Drop Calculator (Single-Phase)

Voltage drop is a critical factor in electrical system design and installation. It refers to the reduction in voltage as electrical current flows through a conductor due to its resistance. Excessive voltage drop can lead to poor equipment performance, overheating, reduced efficiency, and even equipment failure.
This Voltage Drop Calculator helps estimate the voltage drop in a single-phase circuit using cable length, current, and conductor size. It is widely used by electrical installers, site engineers, and students to ensure compliance with electrical standards and good engineering practice.

What Is Voltage Drop?

Voltage drop occurs because every conductor has resistance. When current flows through a conductor, energy is lost as heat, causing a reduction in voltage between the source and the load. Mathematically, voltage drop depends on:

• Length of the conductor
• Cross-sectional area of the conductor
• Current flowing through the conductor
• Material resistivity (copper or aluminum)

If voltage drop is too high, electrical loads may not receive the required operating voltage.

How to Use the Voltage Drop Calculator

Where:
• L = One-way cable length (meters)
• I = Current (amperes)
• ρ = Resistivity of conductor (Ω·mm²/m)
• A = Cross-sectional area (mm²)

The factor of 2 accounts for the round-trip length (phase and neutral).

Recommended Voltage Drop Limits

Common practice limits voltage drop to:
• 3% for lighting circuits
• 5% for power circuits
Exceeding these limits may cause performance and safety issues.

Applications of Voltage Drop Calculation

• Cable sizing and selection
• Electrical installation design
• Energy efficiency improvement
• Compliance with wiring regulations
• Troubleshooting low-voltage problems

Common Mistakes

• Ignoring round-trip length
• Using incorrect conductor material
• Neglecting current increase under load
• Using undersized cables