Electrical Engineering Tool

Cable Sizing & Voltage Drop Calculator

Calculate optimal cable size for your electrical installation. Determine voltage drop, power loss, and ensure compliance with IEC/NEC standards. Essential for solar PV, EV chargers, and industrial applications.

Input Parameters

Electrical Load

Voltage (V)230
System voltage (line-to-neutral for 1Φ, line-to-line for 3Φ).
Current (A)32
Load current or circuit breaker rating.
Power factor0.85
For DC or resistive loads, use 1.0.
Cable length (m)50
One-way distance (not round-trip).

Cable Properties

Conductor material
Conductor size
Ambient temperature (°C)30
Max voltage drop (%)3
IEC recommends 3-5%. Solar PV: 2-3%.
Tip: For solar PV systems, keep total voltage drop (DC + AC) under 3%. For long cable runs, consider upgrading to the next size up.

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Frequently Asked Questions

What voltage drop percentage is acceptable?
IEC 60364 recommends max 4% for lighting and 5% for other loads. For solar PV, best practice is 2-3% total (DC + AC combined). Sensitive electronics may require <2%.
How do I choose between copper and aluminum?
Copper has 60% better conductivity and is preferred for most applications. Aluminum is cheaper and lighter, making it suitable for long overhead lines and larger industrial cables (≥35mm²).
Why is the round-trip length used for DC systems?
In DC circuits, current flows through both positive and negative conductors, so voltage drops occur in both. The formula accounts for this by using 2× the one-way length (or you provide one-way and we calculate internally).

The Engineering Science of Cable Sizing

Selecting the correct cable size is not just about meeting code requirements; it is a critical factor in the safety, efficiency, and longevity of any electrical installation. Whether designing for residential solar PV systems, EV charging stations, or heavy industrial machinery, undersized cables can lead to dangerous overheating, fire hazards, and significant energy losses.

Understanding Voltage Drop

Voltage drop occurs when the internal resistance of the cable causes the voltage at the load end to be lower than at the source. This is defined by Ohm's Law (V = I × R). Excessive voltage drop can cause motors to overheat, lights to flicker, and sensitive electronics to fail. The IEC 60364 standard typically recommends a maximum voltage drop of 3% to 5% depending on the circuit type, while NEC has similar recommendations for Branch Circuits and Feeders.

Key Factors in Calculation

This Cable Sizing & Voltage Drop Calculator simplifies these complex engineering decisions, ensuring your installation is safe, efficient, and compliant with global best practices.