Circle Calculator
Calculate the area, circumference, diameter, and radius of any circle with our easy-to-use calculator.
Circle Calculator
Calculating circle properties…
Calculation Results
Circle Visualization
Circle Formulas
Frequently Asked Questions
A circle is a shape consisting of all points in a plane that are at a given distance from a given point, the center. The distance between any point of the circle and the center is called the radius. Circles are simple closed curves that divide the plane into two regions: the interior and the exterior.
The radius is the distance from the center of the circle to any point on its circumference. The diameter is the distance across the circle passing through the center, connecting two points on the circumference. The diameter is always twice the length of the radius (d = 2r).
Pi (Ï€) is a mathematical constant representing the ratio of a circle’s circumference to its diameter. It is an irrational number, meaning it has an infinite number of decimal places without repeating. The value of pi is approximately 3.14159, but it is often rounded to 3.14 for simple calculations.
The area of a circle is calculated using the formula A = π × r², where A is the area and r is the radius. First, square the radius (multiply it by itself), then multiply the result by pi (approximately 3.14159). Our circle calculator can do this calculation for you automatically.
The circumference of a circle is calculated using the formula C = 2 × π × r, where C is the circumference and r is the radius. Multiply the radius by 2, then multiply the result by pi (approximately 3.14159). Alternatively, you can use the diameter with the formula C = π × d, where d is the diameter.