Circle Calculator
Area = πr²; Circumference = 2πr; Diameter = 2rArea=π×25≈78.54; Circumference=2π×5≈31.42
Free online tool
Circle Calculator
Enter the radius to find all circle measurements.
Instant calculation
Circle Calculator
Enter the radius to find all circle measurements.
Your result
Calculation
Your numbers stay in this browser. Nothing is uploaded or saved.
Three clear steps
How to use this calculator
- 01
Enter radius
Type the radius of the circle.
- 02
Calculate
See area, circumference and diameter.
- 03
Use results
All measurements use the same unit as the radius.
The formula
How this calculation works
From the radius, compute the diameter (double), circumference (2πr) and area (πr²).
Check the method
Worked examples
Each example follows the same formula used by the calculator.
Radius 5 — area and circumference?
Area=π×25≈78.54; Circumference=2π×5≈31.42Area≈78.54, Circumference≈31.42Common questions
Questions about this calculation
What is the Circle Calculator?
The Circle Calculator helps you calculate a circle's area, circumference and diameter from its radius. Enter your values and select Calculate to get an instant result.
How is the result calculated?
From the radius, compute the diameter (double), circumference (2πr) and area (πr²).
Can you show an example?
Example: Radius 5 — area and circumference? — Area≈78.54, Circumference≈31.42.
Is my data saved when I use the Circle Calculator?
No. All calculations run locally in your browser. Your inputs and results are never uploaded, stored or shared with anyone.
Is the Circle Calculator free to use?
Yes. The Circle Calculator is completely free. No account, sign-up or payment is required. It works on mobile, tablet and desktop.
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