MihsabaHow to use
A circle is fully determined by one measurement. Choose radius, diameter, circumference or area; the calculator first recovers the radius and then derives the other three measurements using pi.
- Choose the measurement you already know.
- Enter a positive value in your chosen unit.
- Read radius, diameter, circumference and area; area is expressed in the corresponding squared unit.
How it is calculated
Example
Example: radius 5 gives diameter 10, circumference about 31.41592654 and area about 78.53981634. Starting from that area returns radius 5 through √(A/π).
Important notes
The calculator is unit-neutral: if lengths are in centimeters, circumference is in centimeters and area in square centimeters. Decimal results are approximations because pi is irrational; calculations use the full browser Math.PI value before display rounding.
Frequently asked questions
Can I find radius from area?
Yes. Use r = √(A/π).
Are circumference and area the same quantity?
No. Circumference is boundary length; area measures the region inside the circle.
Do I need to select meters or centimeters?
Not for the mathematics. Keep the unit interpretation consistent and remember area uses a squared unit.
Is this calculator free?
Yes. It is free to use and requires no account.