What a circle sector is
A sector is the pie-slice shaped region of a circle bounded by two radii and the arc between them. Its area is a fraction of the whole circle’s area, based on how large the central angle is compared to a full 360-degree turn: Area = (angle / 360) × π × r².
How this calculator works
Enter the circle’s radius and the sector’s central angle in degrees. The calculator finds the sector area, the length of the curved arc, and the total perimeter of the sector (the arc plus the two straight radius edges).
An angle of 360 degrees represents the full circle. This tool is for general math and educational use.
Last reviewed August 2026