Circle Calculator

Which measurement of the circle you already know. Any single one determines the whole circle, so all the others are computed from it.

• Radius: centre to edge.
• Diameter: edge to edge through the centre (2r).
• Circumference: the distance around (2πr).
• Area: the enclosed surface (πr²).

The numeric size of the chosen quantity, in any length (or squared length, for area) unit. It must be positive.

An angle at the centre of the circle, in degrees. If given, the tool also computes the arc length, chord, sector area and segment area it cuts out.

Example: 90 gives a quarter of the circle.