How do I find a circle's area?
Multiply pi by the radius squared. With a radius of 5, the area is pi times 25, about 78.5. The radius is the distance from the centre to the edge.
// maths › 2D Shapes
Circle Area Calculator
Find a circle's area, circumference, diameter and radius. Enter any one of these and the rest are worked out.
area = πr² ; circumference = 2πr ; diameter = 2r
Frequently asked questions
Can I solve from the diameter or circumference?
Yes. This calculator lets you enter any one of radius, diameter, area or circumference, and it works out the rest. Diameter is just twice the radius.
What is the difference between circumference and area?
Circumference is the distance around the circle (a length); area is the space inside it (a square measure). They use different formulas: 2 pi r versus pi r squared.
What is pi?
The ratio of any circle's circumference to its diameter, roughly 3.14159. It appears in every circle formula because all circles share this same proportion.
Where is this used?
Sizing a circular table or rug, working out pizza value for money, pipe cross-sections, or how much edging a round garden bed needs.