Circle Calculator
Calculate the area, circumference, diameter, and radius of a circle given any one of these values.
Circle Parameters
units
units
units
units²
Circle Formulas
The relationships between a circle's radius, diameter, circumference, and area are fundamental in geometry.
Key Formulas:
- Diameter: d = 2r
- Circumference: C = 2πr = πd
- Area: A = πr2 = π(d/2)2
Where:
- r = Radius
- d = Diameter
- C = Circumference
- A = Area
- π ≈ 3.1415926535... (Pi)
Circle Properties Examples
| Radius (r) | Diameter (d) | Circumference (C) | Area (A) |
|---|---|---|---|
| 1 | 2 | 6.28 | 3.14 |
| 5 | 10 | 31.42 | 78.54 |
| 10 | 20 | 62.83 | 314.16 |
Frequently Asked Questions
What is a circle?
A circle is a round plane figure whose boundary (the circumference) consists of points equidistant from a fixed central point.
What is the difference between radius and diameter?
The radius (r) is the distance from the center of the circle to any point on its circumference. The diameter (d) is the distance across the circle passing through its center, which is twice the radius (d = 2r).
What is Pi (π)?
Pi (π) is a mathematical constant that represents the ratio of a circle's circumference to its diameter, approximately 3.14159. It is a fundamental constant in mathematics and physics.