Circle Circumference Calculator Formula

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

Use the Circle Circumference Calculator

Formulas Used

Circumference

circumference = 2 * pi * r

Area

area = pi * r^2

Diameter

diameter = 2 * r

Variables

VariableDescriptionDefault
rRadius7

How It Works

How to Calculate the Circumference of a Circle

Formula

C = 2 × π × r

Or equivalently: C = π × d (where d is the diameter)

Where:

  • C = Circumference
  • π ≈ 3.14159
  • r = radius
  • d = diameter (2r)

    • Worked Example

    Find the circumference of a circle with radius 7.

    r = 7
    1. 01C = 2 × π × 7
    2. 02= 14π
    3. 03= 14 × 3.14159
    4. 04≈ 43.9823

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