Area Calculator

Calculate area for rectangles, circles, triangles, trapezoids, and other common shapes.

Enter your values

Change any field. The result is recalculated on this device.

Formula, example and assumptions
Area (m²)80

Your result

Local calculation
Area (m²)80

Area measures the surface inside the selected shape. Enter every dimension in the same length unit; the answer uses that unit squared.

Shape
Rectangle
Length unit used for every dimension
Metres
See how this is calculated
Check the inputs and method

These are your current inputs, not the worked example further down the page.

Shape
Rectangle
Length unit used for every dimension
Metres
Length
10
Width
8

Method

Rectangle area = length × width. Circle area = π × radius². Triangle area = base × perpendicular height ÷ 2. Trapezoid area = (parallel side A + parallel side B) × perpendicular height ÷ 2. The output is in the square of the selected length unit.

Read the worked example and assumptions

How this calculation works

Choose the shape that matches the measured surface and enter only its requested dimensions. Area measures two-dimensional coverage, so it is a starting point for estimating paint, floor finishes or a plot section rather than a material quantity by itself. Split an irregular outline into non-overlapping supported shapes, calculate them separately, and subtract openings where appropriate.

Rectangle area = length × width. Circle area = π × radius². Triangle area = base × perpendicular height ÷ 2. Trapezoid area = (parallel side A + parallel side B) × perpendicular height ÷ 2. The output is in the square of the selected length unit.

Worked example

This example uses illustrative inputs. Your current result is shown above.

Choose Trapezoid and metres. Parallel sides of 8 m and 12 m with a perpendicular separation of 6 m give (8 + 12) × 6 ÷ 2 = 60 m². The 6 m measurement is the perpendicular distance, not a sloping side.

Assumptions and limits

  • All dimensions use the same selected length unit; choosing another unit relabels the measurements rather than converting previously entered values.
  • Shapes are planar and geometrically regular. Curves other than circles, slopes, overlaps and material waste are not automatically added.

Questions people ask

Should I enter diameter or radius for a circle?

Enter radius, half the diameter. Substituting diameter would multiply the area by four.

How do I measure an L-shaped room?

Divide it into rectangles without overlap, add their areas, and subtract any excluded portion. Quantity and waste planning belong in the material-specific tools.

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