Circle Area Calculator
Circle area calculator
Solve circle area from radius, diameter, or circumference with linked metrics.
InputsForm2 fieldsLive
Result
78.53981634 sq units
Radius 5, diameter 10, circumference 31.41592654. Uses A = pi × r^2.
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Formula
A = pi x r^2 Symbol legend
| Symbol | Meaning | Unit | Copy |
|---|---|---|---|
A | Circle area | square units | |
r | Circle radius | length | |
\pi | Pi constant (approximately 3.14159) | - |
- Square the radius value.
- Multiply the squared radius by pi.
- Report the result in square units.
Example
Worked example: r = 5
- 1 r^2 = 25
- 2 A = pi x 25
- 3 A = 78.5398
The area is about 78.5398 square units.
How
- Enter the circle radius.
- Review the live area output.
- Copy the result or reset to default values.
Avoid
- Using diameter directly as radius without dividing by 2.
- Confusing circle area formula with circumference formula.
- Rounding pi too aggressively in intermediate steps.
FAQ
Can I enter diameter instead of radius?
This tool uses radius directly. Divide diameter by 2 first.
Why is the result in square units?
Area measures surface size, so units are squared.
Is pi fixed in this calculator?
Yes, it uses JavaScript Math.PI for full floating-point precision.
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