Circle Calculator

Enter a radius, diameter, circumference or area and get the other three circle measurements instantly.

I know the Value

Enter a radius, diameter, circumference or area and get the other three circle measurements instantly.

Formula

Diameter = 2r. Circumference = 2 x pi x r. Area = pi x r squared.

Example

Radius 5 gives diameter 10, circumference 31.42 and area 78.54.

How to use it

Choose which measurement you know.
Enter its value.
Press Calculate.
Read the radius, diameter, circumference and area.

Frequently asked questions

Do I have to enter the radius?

No. Enter any one of radius, diameter, circumference or area and the rest are worked out from it.

What value of pi is used?

The full double precision value of pi, with results rounded to two decimals for display.

Can I use other units?

Yes, as long as one unit is used consistently. The outputs are in the same unit, or square units for area.

Embed this tool

Copy the code below to show this tool on your own website, free, with TinyExe branding and a link back.

Size

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Circle Calculator

Formula

Example

How to use it

Frequently asked questions

Embed this tool

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