Area Calculator
Find the area of a rectangle, triangle, circle, parallelogram, trapezoid, or ellipse from its dimensions. Calculates in your browser.
Area
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Show the math
Each shape has its own area formula:
rectangle = length × width
triangle = ½ × base × height
circle = π × radius²
trapezoid = ½ × (a + b) × height
ellipse = π × a × b
Keep every length in the same unit and the area comes out in that unit squared, feet give square feet, metres give square metres. All math runs locally in your browser.
What this does
An area calculator finds the area of common 2D shapes (rectangle, triangle, circle, parallelogram, trapezoid, and ellipse) from the dimensions you enter. The result is in square units of whatever unit you use.
How to use it
- Choose the shape.
- Enter the required dimensions.
- Read the area in square units.
How it works
Each shape has its own formula. Lengths share one unit, so the area comes out in that unit squared, enter feet to get square feet, metres to get square metres.
rectangle = length × width; circle = π × radius²
Understanding your result
The area is only as consistent as your units: mix feet and inches and the answer is meaningless, so convert everything to a single unit first. For a circle the radius is half the diameter, and the area grows with the square of the radius, so doubling the radius quadruples the area.
Example
A circle with a 5 ft radius has an area of about 78.5 sq ft (π × 5²).
Sources & methodology
Last updated .
Frequently asked questions
Which shapes are supported?
Rectangle (and square), triangle, circle, parallelogram, trapezoid, and ellipse. Pick the shape and enter the dimensions it needs.
What units does it use?
Whatever unit you enter. All lengths must share the same unit, and the area is that unit squared, feet give square feet, metres give square metres.
How is a circle’s area found?
Area = π × radius². The radius is half the diameter, so halve the diameter first if that is what you measured.
Do you store my numbers?
No. Everything is calculated locally in your browser.
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