Use Ohm’s law: V = I × R
Identify the current through the resistor, I, in amperes
Identify the resistor value, R, in ohms
Multiply current by resistance
The result is the voltage drop across the resistor, V, in volts
If the circuit has multiple resistors, find the current through the specific resistor first
For series circuits, the same current flows through each resistor
For parallel circuits, the voltage drop across each branch resistor is the same as the branch voltage
Rearrange Ohm’s law if needed: I = V ÷ R or R = V ÷ I