Circles - Calculating Area and Circumference

The Area of a Circle is calculated using this formula: The Circumference of a Circle is calculated using this formula:  or Important things to remember:

Circle

Circle
The red line represents the diameter. The diameter is the distance of the widest part of the circle, from any point of the edge of the circle to the opposite side. The green line represents the radius (the distance from the centre of the circle to the outer edge).