Estimate voltage drop for a cable of a given size, or find a recommended cable size that keeps voltage drop within a safe limit for your load, cable length, and material. This is a simplified estimation tool — always confirm final cable sizing against local electrical code, installation standards, and a qualified electrician.
How to Use This Calculator
Choose whether you want a recommended cable size, or the voltage drop for a cable size you already have.
Enter voltage, phase, cable material, and cable length (one-way run length).
For cable size mode, enter your load, power factor, and the maximum voltage drop % you'll allow (3% is a common general guideline). For voltage drop mode, enter the current and cable size directly.
Frequently Asked Questions
Single-phase: Vd = (2 × ρ × L × I) ÷ A. Three-phase: Vd = (√3 × ρ × L × I) ÷ A, where ρ is the cable material's resistivity, L is length in metres, I is current in amps, and A is the cable cross-section in mm².
Aluminium has higher electrical resistance than copper of the same cross-section, so it causes a larger voltage drop and typically needs a larger cable size for the same current and length.
No. This tool gives a simplified estimate for planning purposes only. Actual cable sizing must also account for ambient temperature, installation method, grouping with other cables, and local electrical code — always confirm with a qualified electrician.