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Area Calculator
The area of a rectangle, circle or triangle — enter the dimensions for your shape and see it at a glance.
Only the dimensions for the shape you picked are used; the others are ignored.
Area
How it works
Rectangle: length × width Circle: π × radius² Triangle: ½ × base × height
Worked example: a rectangle 12 m long and 8 m wide has an area of 12 × 8 = 96 m². A circle of radius 5 m is π × 25 = 78.54 m², and a triangle with base 10 m and height 6 m is ½ × 10 × 6 = 30 m².
Frequently asked questions
Should I use the diameter or the radius for a circle?
The radius — half the width across. If you only know the diameter, halve it first: a 10 m diameter means a 5 m radius.
What is the height of a triangle?
The vertical distance from the base to the opposite corner, measured at a right angle to the base — not the length of a sloping side.
How do I convert square metres to square feet?
Multiply by 10.764. So 96 m² is about 1,033 square feet.
What if my measurements are in centimetres?
Convert to metres first (divide by 100), or the area will come out in square centimetres, which is 10,000 times smaller.
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