Circle Area Calculator Formula

Understand the math behind the circle area calculator. Each variable explained with a worked example.

Use the Circle Area Calculator

Formulas Used

Area

area = pi * r^2

Circumference

circumference = 2 * pi * r

Diameter

diameter = 2 * r

Variables

VariableDescriptionDefault
rRadius5

How It Works

How to Calculate the Area of a Circle

Formula

A = π × r²

Where:

  • A = Area
  • π ≈ 3.14159
  • r = radius

    • The area is the space enclosed within the circle.

    Worked Example

    Find the area of a circle with radius 5.

    r = 5
    1. 01A = π × 5²
    2. 02= π × 25
    3. 03= 3.14159 × 25
    4. 04≈ 78.5398

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