What is Ohm’s law?
Ohm’s law describes the relationship between voltage, current and resistance in a simple electrical circuit.
Common Ohm’s law formulas
Current can be calculated as voltage divided by resistance, while resistance can be calculated as voltage divided by current.
Frequently asked questions
What does V = I × R mean?
Voltage equals current multiplied by resistance.
How is power calculated?
Power in watts equals voltage multiplied by current.
Can I leave one field blank?
Yes. Enter any two of voltage, current and resistance and the calculator derives the third.
Using this calculator effectively
Ohm's law relates voltage, current and resistance, while electrical power can be derived from the same values. This calculator is useful for basic circuit analysis when any two compatible quantities are known.
Common uses
- Finding current from voltage and resistance.
- Finding resistance from voltage and current.
- Calculating approximate electrical power from the resulting values.
Tips for a better estimate
- Use compatible units such as volts, amps and ohms.
- Remember that real AC circuits can require impedance and power-factor considerations beyond simple resistance.
- Use measured values carefully because component tolerances can affect the practical result.
Helpful guides
Ohm's Law Explained · Watts, Amps and Volts Explained
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Amps to Watts Calculator · Watts to Amps Calculator · Resistor Color Code Calculator