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Geometry Calculator

Compute area and perimeter of circle, rectangle, triangle and trapezoid.

Circle
Area: 78.5398
Circumference: 31.4159
Rectangle
Area: 40
Perimeter: 26
Triangle (3 sides)
Area: 6
Perimeter: 12
Trapezoid
Area: 30
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Area and perimeter formulas are easy to misremember when you only need them once. Pick a shape, type its dimensions, and get the area and perimeter worked out, so you can size a room, a garden bed or a craft project without digging out a textbook.

4 x 3area 12perim 14
Dimensions → area, perimeter

How to use: Geometry Calculator

  1. 1Enter inputPick the shape section.
  2. 2Set optionsEnter the dimensions.
  3. 3ProcessRead area and perimeter instantly.
  4. 4Get resultCompare multiple shapes at once.

Common use cases

Size a spaceFind the floor area of a room for flooring, paint or carpet.
Plan a gardenWork out the area of a bed for soil, mulch or seed.
Check homeworkVerify a geometry answer for a circle, triangle or rectangle.
Estimate materialsTurn a perimeter into the length of edging or fencing you need.

Good to know

Keep your units consistentMix metres and centimetres and the answer is nonsense. Convert everything to one unit first, then read the result in that unit squared.
Area grows faster than lengthDoubling a square's side quadruples its area, not doubles it. That is why a slightly bigger room needs a lot more flooring.
Rough input, rough outputYour answer is only as precise as the measurements you put in. A tape read to the nearest centimetre cannot give a square-millimetre area.
Real shapes are rarely perfectRooms are not exact rectangles and gardens are not true circles. Measure the real thing and add a margin for offcuts.

Frequently Asked Questions