Circle Calculator

Properties of a Circle

This simple yet powerful calculator helps you find the key properties of a circle from a single measurement: the radius. It instantly calculates the diameter, circumference, and area.

The Circle Formulas Explained

• Radius (r): The distance from the center of the circle to any point on its edge.
• Diameter (d): The distance across the circle passing through the center. d = 2 * r
• Circumference (C): The distance around the circle. C = 2 * π * r
• Area (A): The space inside the circle. A = π * r² Where π (Pi) is a mathematical constant, approximately equal to 3.14159.

How to Use the Calculator

1. Enter Radius: Input the radius of your circle.
2. Calculate: The calculator will immediately display the calculated Diameter, Circumference, and Area.

Real-World Example

You have a circular garden with a radius of 5 meters.

1. Enter 5 in the radius field.
2. The calculator will show:
   • Diameter: 2 * 5 = 10 meters
   • Circumference: 2 * π * 5 ≈ 31.42 meters
   • Area: π * 5² ≈ 78.54 square meters

Frequently Asked Questions (FAQ)

• What if I only know the diameter? Simply divide the diameter by 2 to find the radius, and then enter that value into the calculator.
• What if I only know the circumference or area? You would need to rearrange the formulas to solve for the radius first. For example, if you know the Area (A), r = √(A / π).
• What is Pi (π)? Pi is a special irrational number that represents the ratio of a circle's circumference to its diameter. It's approximately 3.14159, but its decimal representation goes on forever without repeating.