Ohm's Law Calculator
Enter any two values and the other two are calculated.
What is Ohm's Law Calculator
An Ohm's law calculator works out voltage, current, resistance, and power in a DC circuit. Enter any two of the four values and it applies V = I x R along with the power formula P = V x I, plus every derived form, to fill in the missing two right away.
How to use
- Enter any two known values, for example 12 volts and 6 ohms.
- Read the other two results as they fill in automatically.
- Change a field to recalculate from a new pair of values.
- Press Clear to start over with a fresh circuit.
- Copy the link to share the calculation with your numbers ready.
When to use it
Wiring an LED and need to size the resistor? Put in your 12 volt supply and a 6 ohm load and you instantly get 2 amps and 24 watts, so you can check the current stays safe and the resistor is rated for the heat. Handy for hobby electronics, car audio, battery packs, and any DC circuit where you know two numbers and need the rest.
Frequently asked questions
What is Ohm's law?
Ohm's law says that current equals voltage divided by resistance (I = V / R). Adding the power formula P = V x I means that knowing any two of voltage, current, resistance, and power lets you calculate the other two.
Which two values do I need to enter?
Any two of the four. The calculator picks the right formula automatically, whether you know voltage and current, resistance and power, or any other pair.
Does this work for AC circuits?
It covers DC circuits and the purely resistive part of AC. Real AC power also depends on phase and power factor, which this calculator does not model.
Why do I sometimes get no result?
Some pairs cannot be solved, such as a current of zero amps, which would make resistance infinite. Enter non-zero values wherever the formula needs to divide.
Can I share this tool with my inputs pre-filled?
Yes. The URL updates automatically as you type. Copy it from the address bar or use the Share button, and anyone who opens the link will see your exact inputs ready to go.
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