Circle Calculator
Calculate radius, diameter, circumference, and area of a circle from any single property.
Calculate From
Circle Diagram
Circle Formulas
Diameter:d = 2r
Circumference:C = 2 x pi x r
Area:A = pi x r^2
Circle Properties
r = 5.0000
rRadius
5.000000
dDiameter
10.000000
CCircumference
31.415927
AArea
78.539816
Quarter Circle (90 sector)
Sector Area
19.6350
Arc Length
7.8540
Quick Reference
| Radius | Circumference | Area |
|---|---|---|
| 1 | 6.28 | 3.14 |
| 2 | 12.57 | 12.57 |
| 3 | 18.85 | 28.27 |
| 4 | 25.13 | 50.27 |
| 5 | 31.42 | 78.54 |
| 10 | 62.83 | 314.16 |
About Circles
Definition
A circle is a shape consisting of all points in a plane that are at a given distance (radius) from a given point (center).
The Value of Pi
Pi is approximately 3.14159265359... It is the ratio of a circle's circumference to its diameter.