Use this geometry calculation when the shape, dimensions, coordinate system, and units match the stated ideal Euclidean model.

Radius

Optional number input.

Diameter

Optional number input.

Circumference

Optional number input.

Area

Optional number input.

Calculate a circle's radius, diameter, circumference, and area from one known measurement. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Radius

The resulting radius returned as a number.

Diameter

The resulting diameter returned as a number.

Circumference

The resulting circumference returned as a number.

Area

The resulting area returned as a number.

• The result assumes exact idealized geometry. Measurement uncertainty, rounded inputs, nonplanarity, self-intersection, thickness, curved coordinate systems, and ambiguous dimension definitions are not automatically represented.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Sketch and label the dimensions, verify unit consistency, and use coordinate or CAD methods for irregular measured shapes.

• Circle Sector Area Calculator

  Compute the area of a circular sector from its central angle and radius.

• Annulus Area Calculator

  Calculate the area of an annulus from its outer and inner radii as π(R²−r²).

• Circle Arc Length Calculator

  Compute the arc length of a circular segment from its central angle and radius.