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Circle Calculator
Solve all measurements of a circle by entering any single known value: radius, diameter, circumference, or area.
Enter Known Value
Results
| Radius (r) | — |
|---|---|
| Diameter (d) | — |
| Circumference (C) | — |
| Area (A) | — |
Understanding Circle Equations
A circle is a round, two-dimensional shape where all points on its boundary are equidistant from a central point.
The Key Components
- **Radius (r):** The distance from the center of the circle to any point on its outer edge.
- **Diameter (d):** The straight-line distance across the circle through its center. It is always exactly twice the radius ($d = 2r$).
- **Circumference (C):** The perimeter or boundary length of the circle. It is defined as $C = 2\pi r$.
- **Area (A):** The total 2D space enclosed within the circle's boundary. It is defined as $A = \pi r^2$.
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