Area calculator
Pick a shape and a unit, then enter the measurements.
What you enter stays on this page and is not sent anywhere.
Enter the measurements to see the result.
How to use it
- Choose the shape and the length unit.
- Enter each measurement. A circle can use the radius or the diameter.
- Read the area and the perimeter, with square metres and square feet.
Questions
Which formulas are used?
Rectangle: length times width. Circle: pi times radius squared. Triangle: half of base times height, or Heron's formula from three sides. Trapezoid: average of the two bases times height.
Why is there no perimeter for some shapes?
A triangle given by base and height, a trapezoid or a parallelogram does not fix its slanted sides, so the perimeter cannot be found. Use the three-sides triangle if you need it.
How accurate is the ellipse perimeter?
The ellipse area is exact. Its perimeter has no simple exact formula, so it is a very close approximation (Ramanujan), shown with a ≈ sign.
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