Geometry Calculator
Area and perimeter for a circle, rectangle or triangle.
What is a geometry calculator?
A geometry calculator works out the area and perimeter of shapes. Choose a circle, rectangle or triangle, enter the measurements, and get the area and perimeter instantly — with the working shown step by step.
How to use the geometry calculator
Pick the shape, enter its measurements (for a circle, just the radius), and click Calculate. The calculator shows the area and the perimeter or circumference, plus the working.
Formula
Circle: Area = πr² and Circumference = 2πr. Rectangle: Area = length × width and Perimeter = 2 × (length + width). Triangle: Area = ½ × base × height and Perimeter = a + b + c.
Example
Circle with radius 5: Area = π × 5² = 78.539816 and Circumference = 2 × π × 5 = 31.415927.
Frequently Asked Questions
What is the area of a circle with radius 5?
The area is 78.539816. Try it on the calculator above — set Shape to Circle and Radius to 5.
How do you find the circumference of a circle?
Multiply 2 × π × radius. For radius 5, the circumference is 31.415927.
What is the area of a rectangle?
Multiply length by width. For example, a rectangle 6 by 4 has an area of 24.
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