CalcArcade.

Area Calculator

Choose a shape, pick your unit and enter the measurements. You get the area and, for rectangles, circles and ellipses, the perimeter as well.

Your numbers

Result

How we calculate it

Rectangle: width × height. Triangle: base × height ÷ 2. Circle: π × radius². Trapezoid: (a + b) ÷ 2 × height. Parallelogram: base × height. Ellipse: π × a × b, where a and b are half of the two widths.

The perimeter of a rectangle is 2 × (width + height) and the circumference of a circle is 2 × π × radius. An ellipse has no simple exact perimeter, so Ramanujan’s approximation is used: π × (3 × (a + b) − √((3a + b) × (a + 3b))). A 5 by 3 rectangle has an area of 15 and a perimeter of 16.

Assumptions and limits

  • Height always means the straight distance between the base and the opposite side, not the length of a slanted side.
  • The area is in your unit squared, for example m² or ft².
  • The ellipse perimeter is an approximation, accurate to a tiny fraction for most shapes.

Frequently asked questions

How do I find the area of a triangle?

Multiply the base by the height and divide by 2. The height is measured at a right angle to the base, so a base of 10 and a height of 6 give an area of 30.

What is the difference between area and perimeter?

Area is the amount of surface inside a shape, measured in square units. Perimeter is the distance around the outside, measured in plain units.

How do I find the area of an irregular shape?

Split it into rectangles, triangles and other simple shapes, find each area here and add them up. For a floor plan, the square footage calculator does this for room shapes.

Related calculators

Worked example (a fixed example using the starting numbers, it does not change as you type)

Inputs: Shape = Rectangle; Unit = meters (m); Width = 5; Height = 3.

  • Area 15 m²
  • Perimeter 16 m

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Last reviewed: . Formulas and assumptions are described on our methodology page. For information only; not professional advice.