Circle Calculator - Calculator See


Circle Calculator

Calculate radius, diameter, circumference, and area of a circle from any single known measurement.

Calculator Inputs

Distance from center to perimeter.

Calculated Results

Circle Area
78.540 sq units
Circumference 31.416 units
Diameter 10.000 units
Radius 5.000 units
Values calculate live as you adjust inputs.

About Circle Calculator

Calculates geometry properties of a circle using the mathematical constant pi (3.14159…).

What is Circle Calculator?

Calculates geometry properties of a circle using the mathematical constant pi (3.14159...).

How to Use This Calculator

  1. Enter circle radius.
  2. View calculated circumference, diameter, and surface area.

The Mathematical Formula & Variables

Area = pi * r^2; Circumference = 2 * pi * r; Diameter = 2 * r

Step-by-Step Worked Example

Scenario: Circle with radius r = 5.

  1. Diameter = 2 * 5 = 10.
  2. Circumference = 2 * pi * 5 = 31.416.
  3. Area = pi * 5^2 = 25 * 3.14159 = 78.54.

Result: 78.540 sq units

Frequently Asked Questions

What is the relationship between circumference and diameter?

Dividing the circumference of any circle by its diameter always equals exactly pi (π ≈ 3.14159).