Voltage Drop Calculator
Voltage Drop Calculator
Enter cable length (one-way), load current and cable size, and we’ll estimate voltage drop and percentage drop for a single-phase run (there and back).
Guidance only: many installers aim for ≤3% drop for lighting circuits and ≤5% for general power. Real-world results vary with temperature, cable type and installation method.
Vdrop = 2 × L × I × R
%drop = (Vdrop ÷ Vsupply) × 100
(L = one-way length in metres, I = current, R = cable resistance per metre)