Area Calculator
Areas of circles, triangles, trapezoids and six more shapes.
Which dimensions to enter depends on the shape: Circle – Dim 1 = radius. Rectangle – length, width. Square – side. Triangle – base, height. Parallelogram – base, height. Trapezoid – side a, side b, height (Dim 3). Ellipse – semi-axis a, semi-axis b. Sector – radius, angle in degrees.
Frequently Asked Questions
What is the formula for the area of a trapezoid?
Average the two parallel sides and multiply by the height: A = (a + b) / 2 x h. It works because a trapezoid can be rearranged into a rectangle of that width and height.
How do I find the area of a sector?
Take the fraction of the full circle given by the angle: (angle / 360) x π r². A 90-degree sector is exactly a quarter of the circle area.
Do the units matter?
The formula is unit-agnostic: enter all dimensions in the same unit (metres, feet, centimetres) and the answer is in that unit squared. Mixing units gives a meaningless result.
Is the Area Calculator free, and is my data private?
Yes. It is completely free and every calculation runs locally in your browser, so the numbers and dates you enter are never uploaded, stored, or shared with anyone.
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