Maths Geometry
Area calculator
Shape
Length
Width
Area 96
12 × 8
Perimeter 40
If those were metres, in sq ft 1,033.34
Half the area 48
Answer is in the entered unit, squared
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320 × 100
Area formulas by shape: rectangle is length × width, circle is πr², triangle is half base × height, trapezoid is half the sum of the parallel sides × height, and ellipse is π × the two semi-axes multiplied.
How to calculate area
1 Pick the shape.
2 Enter its dimensions in whatever unit you like — the answer is in that unit squared.
3 Read the area and, where it applies, the perimeter.
4 For an irregular shape, split it into these shapes and add the areas.
The one that catches people out is the ellipse perimeter, which has no exact closed form at all — it needs an elliptic integral. Ramanujan published an approximation in 1914 that is accurate to better than one part in ten million for anything but the most extreme ellipse, and that is what is used here. It is a nice reminder that "simple shape" and "simple formula" are not the same thing: the area of an ellipse is trivial and its perimeter is genuinely hard.
Questions
π times the radius squared. A radius of 5 gives 78.54.
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300 × 250
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