Area Calculator

This area calculator finds the area of a rectangle, square, triangle, circle, ellipse, trapezoid, parallelogram or circle sector. Pick a shape, choose a unit, type the sizes and read the answer. The working is shown under the result, and the area is also given in other units.

40 ft²length × width = 8 × 5 = 40

The same area in other units

Use the same unit for every size. Results show up to four decimal places, or four significant digits for very small numbers.

How to use the area calculator

  1. Pick a shape from the first list.
  2. Choose the unit your sizes are in, such as feet or centimeters.
  3. Type each size into its box. The answer changes as you type.
  4. Read the area in the highlighted box. The same area in other units is listed under it.

Area formulas for each shape

  • Rectangle: length × width.
  • Square: side × side.
  • Triangle: base × height ÷ 2.
  • Triangle from three sides (Heron formula): the square root of s × (s minus a) × (s minus b) × (s minus c), where s is half the sum of the three sides.
  • Circle: π × radius × radius.
  • Ellipse: π × a × b, where a and b are the two half-widths.
  • Trapezoid: (a + b) ÷ 2 × height, where a and b are the two parallel sides.
  • Parallelogram: base × height.
  • Circle sector: angle ÷ 360 × π × radius × radius.

Area examples

A room that is 12 ft long and 10 ft wide has an area of 12 × 10 = 120 ft². A circle with a radius of 4 m has an area of π × 4 × 4 = 50.27 m². A triangle with a base of 10 cm and a height of 6 cm has an area of 10 × 6 ÷ 2 = 30 cm².

Area units and how they relate

Area is always written in square units, such as m² or ft². One square meter is about 10.764 square feet. One acre is 43,560 ft², which is about 4,046.86 m². One hectare is 10,000 m². The list under the result shows your answer in each of these units.

How to find the area of an odd shape

Split the shape into parts you know, such as rectangles and triangles. Find the area of each part with this calculator, then add the results together. To find the area of an L shaped room, split it into two rectangles.

Common area questions

How many square feet are in a room that is 14 ft by 12 ft? Multiply the two sizes: 14 × 12 = 168 ft². To find square yards for carpet, divide square feet by 9, because one square yard is 9 ft². A room of 12 ft by 15 ft is 180 ft², which is 20 yd².

For paint, find the area of each wall as a rectangle, add the walls together and take away the area of doors and windows. For a lawn or a garden, split the plot into simple shapes and add the parts.

Area is not the same as perimeter. Perimeter is the distance around a shape, while area is the space inside it.

Frequently asked questions

What does area mean?

Area is the amount of flat space inside a shape. It is measured in square units such as square feet or square meters.

Why is area in square units?

Area multiplies two lengths. A rectangle that is 5 m by 3 m has an area of 5 m × 3 m = 15 m².

Can I mix units, such as feet and inches?

No. Use one unit for every size. Change the smaller sizes into the larger unit first. For example, 6 in is 0.5 ft.

Why does the triangle with three sides show an error?

The three sides must be able to meet. Any two sides must add up to more than the third side. If they do not, no triangle can be drawn.

How many decimal places does the area calculator show?

Results show up to four decimal places, or four significant digits for very small numbers.

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