Ohm's Law Calculator
Calculate voltage, current or resistance using Ohm’s law.
Ohm's Law Calculator
How to use the Ohm's Law Calculator
Select the quantity you need, enter the other two electrical values, and calculate the result.
How it works
Ohm’s law describes the relationship between voltage, current and resistance: V = I × R. Select the quantity you want to find, then enter the other two values in volts, amperes and ohms.
Example: A current of 2 A through a resistance of 10 Ω requires 20 V. The same relationship can be rearranged as I = V ÷ R or R = V ÷ I.
What to keep in mind
The calculation assumes an ideal resistive circuit. Real components have tolerances, power limits and temperature effects. Isolate equipment and follow appropriate electrical-safety procedures before taking measurements or changing a circuit.
Frequently asked questions
Does Ohm’s law apply to AC circuits?
It applies directly to purely resistive AC circuits using compatible RMS values. Reactive circuits require impedance rather than resistance alone.
How do I calculate power?
For a resistive circuit, power can be calculated using P = V × I after finding voltage and current.
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