Rectangle area 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
A = l × w
Where this usually goes wrong
Both sides in the same unit, and the answer is in that unit squared.
Worked example
12 by 5 is an area of 60.
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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