# Circle Area & Circumference Calculator

Calculator

Circle Area & Circle Circumference Calculator from radius or diameter. Our calculator computes circle circumference and area using various common units of measurement. Would you like to know the area or the circumference of a circle and the only piece of information you have is the radius or diameter of the circle? You are only one click far from the solution.

Q&A

## How to use the Circle Area & Circumference Calculator?

The use of the Circle Area & Circumference Calculator is really easy: enter the diameter or the radius of the circle, the result appears immediately.

## How to calculate the circle area and circumference

### Formulas used for the calculation of a circle’s circumference and area from diameter

• The formula used for the calculation of circumference: C = d ∙ π
• The formula used for the calculation of area: A = (d/2)2 ∙ π

### The formula used for the calculation of a circle’s circumference and area from radius

• The formula used for the calculation of circumference: C = 2 ∙ r ∙ π
• The formula used for the calculation of area: A = r2 ∙ π

## What is Pi or π?

π is a mathematical constant, approximately equal to 3.1415926535. It is defined in Euclidean geometry as the ratio of a circle’s circumference to its diameter, and also has various equivalent definitions. The number appears in many formulas in all areas of mathematics and physics.