Calculate the area, circumference, and diameter of a circle from its radius.
| Area | – |
| Circumference | – |
| Diameter | – |
Use this calculator to find the area, circumference, and diameter of a circle from a single radius. It is useful for round tables, pipes, garden beds, lids, and any other circular shape measured from the centre to the edge.
The formulas are: area = π r², circumference = 2 π r, and diameter = 2 r. Enter the radius in any length unit you prefer, such as centimetres, metres, or inches, and keep that unit throughout. Area is then expressed in the corresponding square unit (cm², m², in²).
Radius: Distance from the centre of the circle to the edge.
Area: The interior of the circle, π times the square of the radius.
Circumference: The length of the outer edge, equal to π times the diameter.
Diameter: The full width through the centre, twice the radius.
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