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Circle Area calculator
Find the area of a circle from its radius, along with the circumference and diameter.
Circle Area calculator
Enter your values below and press Calculate to see your result instantly.
Formula: a = π×
²
Radius Vector (r)
Computed Absolute Area (A)
314.16 Units²
CIRCUMFERENCE (PERIMETER)
62.83 Units
DIAMETER DEVIATION
20 Units
10
Calculations complete.
About the Circle Area calculator
Find the area of a circle from its radius, along with the circumference and diameter.
How to use the Circle Area calculator
- Enter the Radius (r).
- Press Calculate Circle Plane.
Formula and method
A = π × r², circumference C = 2πr and diameter d = 2r.
Worked example
A circle with radius 5 has an area of 78.54 square units. With radius 10 the area is 314.16.
Tips
- If you know the diameter, halve it to get the radius.
- Doubling the radius makes the area four times bigger.
Frequently asked questions
What is pi?
The ratio of a circle's circumference to its diameter, approximately 3.14159.