Electrical power 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
P = VI
Where this usually goes wrong
Pairs with Ohm’s law: if you have two of voltage, current and resistance, you can get power from either.
Worked example
A 230 V bulb drawing 0.43 A uses about 100 W.
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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