Ohm's law calculator
Fill in what you know and leave the unknown box empty — it works out whichever one is missing. Nothing is uploaded; the arithmetic happens in your browser.
The formula
V = IR
Where this usually goes wrong
Volts, amps, ohms. Milliamps must be divided by 1000 first.
Worked example
12 V across 100 Ω draws 0.12 A.
Those numbers are already in the boxes above — press Work it out to see it, then change them for your own.
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