Area Calculator
Area of a circle, rectangle, triangle or trapezoid from its dimensions.
Enter values
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Step by step
The formula
circle: πr² · rectangle: l×w · triangle: ½bh · trapezoid: ½(a+b)h
Every area formula reduces to the same idea: how many unit squares fit inside. A rectangle multiplies its sides directly, a triangle fills half its bounding rectangle, and a trapezoid behaves like a rectangle whose width is the average of its two parallel sides.
All calculations run locally in your browser and update instantly as you type.
Example calculations
Common questions this calculator answers — select one to load its values.
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Frequently asked questions
Which dimensions do I enter for each shape?+
Circle: A = radius. Rectangle: A = length, B = width. Triangle: A = base, B = height. Trapezoid: A and B = the two parallel sides, C = height. Unused fields are ignored.
What units does this use?+
Any unit you like — the area is in that unit squared. Enter metres to get m², feet to get ft², and so on.
All calculations run locally in your browser. Nothing you type is sent to a server.