Ohm's Law Calculator
Solve for voltage, current or resistance in a circuit using Ohm's Law (V = I × R).
- Voltage12 V
- Current2 A
- Resistance6 Ω
V = I × R: 12 V = 2 A × 6 Ω — all three quantities are locked together by Ohm's Law.
ƒShow your work
- 1V = I × R = 2 A × 6 Ω = 12 V
About the Ohm's Law Calculator
This calculator solves Ohm's Law — the relationship V = I × R between voltage, current and resistance — for whichever of the three values you're missing. Pick what you want to solve for, enter the other two, and it does the division or multiplication for you.
It's a first-week concept in any electronics course, but it stays useful well past the classroom: sizing a resistor for an LED circuit, checking whether a component can handle the current a circuit will actually draw, or just verifying a hand calculation before building something.
Because it's pure arithmetic on three related quantities, the result updates instantly with no data leaving your browser.
How it’s calculated
Ohm's Law states that voltage equals current times resistance (V = I × R) for a simple resistive circuit. Rearranging that same relationship gives the other two forms: current equals voltage divided by resistance (I = V ÷ R), and resistance equals voltage divided by current (R = V ÷ I) — the calculator just picks whichever rearrangement matches what you're solving for.
Frequently asked questions
What is Ohm's Law used for in practice?
It's the basic relationship for sizing components in any resistive circuit — figuring out what resistor value limits current to a safe level for an LED, checking a fuse or wire's current rating against expected load, or working backward from a measured voltage and resistance to find current draw.
Does Ohm's Law apply to AC circuits with capacitors and inductors?
Not directly in this simple form — capacitors and inductors introduce reactance, which behaves differently from plain resistance and requires impedance calculations instead. This calculator's V = I × R form applies cleanly to DC circuits and purely resistive AC loads.
How do I find power (watts) from these values?
Power isn't part of Ohm's Law directly, but it's closely related: P = V × I. Once you know any two of voltage, current and resistance from this calculator, you can multiply voltage by current to get power in watts.
Why is my calculated current higher than what a component is rated for?
That usually means the resistance in the circuit is too low for the voltage applied — Ohm's Law is telling you the circuit will draw more current than the part can safely handle, which is a sign to increase resistance (or reduce voltage) before building it.
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