Circumference & Area Calculator
Compute the circumference and area of a circle from either radius or diameter. This free tool supports your local number format and shows instant results as you type. View the formulas (2πr and πr²), choose units, and copy results in one click.
Number format
Choose how numeric results are displayed. The selected decimal separator (dot or comma) will also be used when parsing input numbers.
What is the circumference of a circle?
The circumference of a circle is the distance around the outer edge or boundary of the circle. It is the total length of the circle's perimeter. The circumference is calculated using the formula:
Circumference = 2 x π x r
where r is the radius of the circle and π (pi) is a mathematical constant that is approximately equal to 3.14.
The circumference is an important property of a circle, and it is used in various mathematical and scientific calculations involving circles, such as finding the length of an arc, the area of a sector, or the volume of a cylinder.
What is the area of a circle?
The area of a circle is the total amount of space inside the boundary or circumference of the circle. It is calculated using the formula:
Area = π x r^2
where r is the radius of the circle and π (pi) is a mathematical constant that is approximately equal to 3.14.