Use the formula: Voltage Drop = Current × Resistance
For DC circuits: Vdrop = I × R
For AC single-phase circuits: Vdrop = 2 × I × R × L
For AC three-phase circuits: Vdrop = √3 × I × R × L
Determine the load current in amperes
Determine the conductor resistance per unit length
Multiply resistance by the total circuit length
Multiply current by total resistance to get voltage drop
Subtract voltage drop from supply voltage to get load voltage
Check that voltage drop is within acceptable limits