Sector Area Calculator

Calculate circle sector area from radius and angle. Free online sector area calculator.

The Sector Area Calculator finds the area of a pie-slice shaped sector of a circle. Using the radius and central angle, this tool calculates the area enclosed between two radii and the arc. Perfect for pizza portion calculations, pie charts, clock faces, and any design involving circular sectors.

Common use cases

  • Pie and pizza slice sizes
  • Chart and graph sectors
  • Windshield wiper coverage
  • Fan blade swept areas
  • Irrigation sprinkler coverage

How to use

  1. Enter the radius of the circle
  2. Enter the central angle (degrees or radians)
  3. Select the angle unit
  4. Click calculate for sector area
  5. View the formula and steps

FAQ

What is the sector area formula?

Area = (θ/360) × πr² (degrees) or Area = ½r²θ (radians), where r is radius and θ is angle.

What fraction of the circle is a sector?

A sector is θ/360 of the full circle (in degrees) or θ/2π (in radians).

How does sector area relate to arc length?

Sector Area = ½ × Arc Length × radius, connecting these two measurements.

What about a semicircle?

A semicircle (180°) has area = ½πr², exactly half the full circle.