Method: DC current = power ÷ system voltage. Cable resistance = resistivity × total circuit length ÷ conductor area. Total circuit length is twice the entered one-way cable length because current travels to the load and returns. Voltage drop = current × cable resistance. Voltage drop percentage = voltage drop ÷ system voltage × 100. Power loss = current² × cable resistance. Copper resistivity is taken as approximately 0.0172 Ω·mm²/m and aluminium as approximately 0.0282 Ω·mm²/m at reference temperature. This calculator checks voltage drop only. Final cable selection must also satisfy conductor ampacity, insulation temperature rating, installation conditions, fault protection and applicable electrical requirements.