A circle is a shape on a plane in which all points are equally distant from the center.

Terms and Symbols Related to Circles

Term Symbol Definition
Area aa The amount of space occupied by the surface of the circle
Circumference cc The perimeter of a circle
Diameter dd The distance of a straight line from one point on a circle to the opposite point on the circle and passes through the center
Pi π\pi The ratio of a circle's circumference to its diameter. Equal to about 22/722/7 or 3.143.14
Radius rr The distance from the center to a point on the edge of a circle

Formulas to Find Properties of Circles

Area of a Circle

a=πr2a = \pi r^2

a=π(d/2)2a = \pi (d/2)^2

Circumference of a Circle

c=2πrc = 2 \pi r

c=dπc = d \pi

Diameter of a Circle

d=2rd = 2r

d=c/πd = c/\pi

Radius of a Circle

r=d/2r = d / 2

r=c/2πr = c/2\pi

Deeper Knowledge on Circles (Geometry)


The angle which subtends an arc equal to the length of the radius of a circle

Broader Topics Related to Circles (Geometry)


The mathematics of shapes

Circles (Geometry) Knowledge Graph