Circle Area Calculator
Enter a radius or diameter to calculate the area of a circle.
Result will appear here.
| Metric | Value |
|---|
Uses Area = πr². If you enter diameter, the tool first converts it to radius.
Privacy: calculations run locally in your browser. No values are stored or transmitted.
How it works
Radius input: Area = πr²
Diameter input: r = d / 2, then Area = πr²
Examples
- radius = 5 → area ≈ 78.54
- diameter = 10 → area ≈ 78.54
FAQ
- What is the formula for circle area?
Area = πr², where r is the radius.
- Can I enter diameter instead of radius?
Yes. This calculator lets you choose radius or diameter as the input type.
- Can the radius be negative?
No. Circle dimensions should be non-negative.
- Are my values stored?
No. Calculations run locally in your browser and are not stored or transmitted.