Ohm’s Law and Power Calculator with Series / Parallel Resistance
Voltage, current, resistance and power from any two values; series and parallel resistance.
Ohm’s law
Enter any two values; the others update.
Resistors in series / parallel
Voltage divider
Frequently asked questions
What is the voltage divider formula?
For two resistors in series, Vout = Vin × R2 / (R1 + R2), where Vout is taken across R2. It holds when the load connected to Vout draws negligible current.
For preliminary assessment only — the final decision must follow the manufacturer’s datasheet and the applicable NEC / IEC / UL standards. Results are calculated from the standard formulas stated on this page and are for design estimates only. They are not a rating of any specific part — always confirm current, voltage, temperature and environment limits against the manufacturer’s datasheet for the part you intend to use.
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