Circle Area Calculator
Calculate the area of a circle from its radius. Also shows circumference and diameter instantly.
Enter the radius of the circle
Area
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Circumference
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Diameter
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Circle Area Formula
A = π × r²
Where r is the radius of the circle. The area represents the total space enclosed within the circle's boundary.
Related Formulas
| Property | Formula |
|---|---|
| Area | A = π × r² |
| Circumference | C = 2 × π × r |
| Diameter | d = 2 × r |
Example: A circle with radius 7 cm
Area = π × 7² = π × 49 ≈ 153.94 cm²
Circumference = 2 × π × 7 ≈ 43.98 cm
Diameter = 2 × 7 = 14 cm
Area = π × 7² = π × 49 ≈ 153.94 cm²
Circumference = 2 × π × 7 ≈ 43.98 cm
Diameter = 2 × 7 = 14 cm
Frequently Asked Questions
How do I find the area of a circle if I only know the diameter?
Divide the diameter by 2 to get the radius, then use A = π × r². Alternatively, use A = π × (d/2)² = π × d² / 4.
What units is the area measured in?
Area is always in square units. If the radius is in centimeters, the area is in cm². If in meters, the area is in m².
Why is π used in circle calculations?
π (pi) is the ratio of a circle's circumference to its diameter. It's approximately 3.14159 and appears naturally in all circular measurements.
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Last updated: 2026-08-08