Circle Area Calculator
Find the area of any circle in seconds. Enter the radius, diameter or circumference, and get the exact area instantly - with the formula steps shown, so students and professionals can follow the working.
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How to use
- Select whether you have the radius, diameter or circumference.
- Enter the value.
- The area will show with formula steps.
Tips
- If you only know the diameter, halve it first - the formula needs the radius.
- For a quick estimate, remember pi is about 3.14.
- Area grows with the square of the radius - doubling the radius quadruples the area.
- Keep your units consistent: radius in cm gives area in square cm.
Note: Formula: Area = pi x r^2, where pi = 3.14159... is used.
Frequently Asked Questions (FAQ)
What can I enter?
The radius, diameter or circumference. The area shows with formula steps.
Which formula is used?
Area equals pi times r squared, with pi equal to 3.14159.
Do I have to halve the diameter myself?
No. Just select the diameter option and enter the value; the calculator handles the conversion to radius for you.
What units should I use?
Keep your units consistent. A radius in cm gives the area in square cm; a radius in meters gives square meters.