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Ohm's law calculator
Voltage, current, resistance and power: enter any two and get the rest.
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About Ohm's law calculator
Enter any two of voltage, current, resistance or power and get the other two. The core relations are V equals I times R and P equals V times I, which give variants such as P equals I squared times R. Useful for checking a circuit, choosing a resistor or sizing a power supply.
How to use Ohm's law calculator
- Enter your numbers above.
- The result updates instantly as you type.
- Change any value to compare different cases.
Why use this tool?
- Private: everything happens in your browser. Nothing you enter is uploaded.
- Free, with no sign-up, no watermark and no limit on how often you use it.
- Works on phones, tablets and computers: Android, iPhone, Windows, Mac and Linux. Nothing to install.
- Available in 10 languages.
Also known as
Frequently asked questions
How do I calculate current from voltage and resistance?
Divide voltage by resistance. A 12 V supply across a 6 ohm resistor gives a current of 2 amps.
Is Ohm's law calculator free?
Yes. Ohm's law calculator on Toolipedia is free to use, with no sign-up and no watermark.
Is it safe to use?
Yes. Everything is worked out in your browser, and nothing you enter is sent to our server.
Does it work on my phone?
Yes. It works in any modern browser on Android and iPhone, as well as on tablets and computers. There's nothing to install.
Do I need an account?
No. Just open the page and use the tool. There's no sign-up and no email needed.