CalcCircle Area Calculator
Last updated: 2026-05-09
The Circle Area Calculator is a free online math calculator. Circle Area Calculator. Free online calculator with formula, examples and step-by-step guide. Get instant results with the detailed formula and step-by-step examples.
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Common Sizes — Click to Fill
| Radius | |
|---|---|
| Triangulo 3m lado | 2.0 |
| Cuadrado 5m lado | 3.5 |
| Pentagono 6m lado | 5.0 |
| Hexagono 8m lado | 7.5 |
| Octogono 10m lado | 12.5 |
How to calculate the area of a circle
The area of a circle is the surface enclosed within the circumference. You need the radius (center to edge) or the diameter (twice the radius). This calculator returns the area, circumference, and diameter instantly.
Circle area formula
Area = π × r²
Where r is the radius and π ≈ 3.14159. If you only have the diameter: Area = π × (d ÷ 2)²
Circumference: C = 2 × π × r
Practical example
Installing a circular pool with a 4 m diameter:
- Radius: 4 ÷ 2 = 2 m
- Area: π × 2² ≈ 12.57 m²
- Circumference: 2 × π × 2 ≈ 12.57 m
Applications
- Construction: Area of circular slabs or foundations.
- Gardening: Surface of circular flowerbeds or ponds.
- Engineering: Cross-section of pipes and columns.
- Math: Geometry problems in school and university.