Area Calculator — Rectangle, Circle, Triangle & More
Calculate the area of any shape: rectangle, square, circle, triangle, trapezoid, and more. Instant results with formula explanations.
What is this calculator?
This area calculator computes the area and perimeter of common geometric shapes: rectangle, square, circle, triangle, trapezoid, and ellipse. It uses standard geometric formulas based on the shape's dimensions, providing instant results with formula explanations.
Formula
For a rectangle: Area = a × b, Perimeter = 2(a + b). Square: Area = a², Perimeter = 4a. Circle: Area = π × a², Perimeter = 2πa. Triangle: Area = 0.5 × a × b, Perimeter = a + b + c (c calculated via Pythagorean theorem if right triangle). Trapezoid: Area = 0.5 × (a + b) × height, Perimeter = a + b + c + d. Ellipse: Area = π × a × b, Perimeter ≈ π[3(a+b) - √((3a+b)(a+3b))].
Example
For a rectangle with a=5 units and b=3 units, the area is 5 × 3 = 15 units², and the perimeter is 2(5+3) = 16 units. For a circle with radius a=4 units, area = π × 4² ≈ 50.27 units², perimeter = 2π × 4 ≈ 25.13 units.
How to use
- 1Select the shape from the dropdown menu. Then enter the required dimensions: for rectangle, enter side lengths a and b; for square, enter side a; for circle, enter radius a; for triangle, enter base a and height b; for trapezoid, enter base a, base b, and height (entered as b); for ellipse, enter semi-major axis a and semi-minor axis b.
- 2Click the Calculate button. The calculator applies the appropriate formula for the selected shape using the entered values and computes the area and perimeter.
- 3The results display the area in square units and the perimeter in units. You can use these values for further calculations, such as material estimation or comparison with other shapes.