Identify the circuit voltage source
Determine the current flowing through the circuit
Measure or find the resistance of the conductor or load
Use the formula: Voltage Drop = Current × Resistance
For AC circuits, use impedance instead of resistance when applicable
For multiple wire runs, calculate the total resistance of the conductors
For parallel circuits, calculate the voltage drop for each branch separately
Subtract the voltage drop from the source voltage to find the load voltage
Verify the result with a multimeter if needed
Compare the calculated drop to the allowable voltage drop for the application