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Circle Sector Area Calculator
Find the area and arc length of a circle sector from its radius and central angle.
Radius
Central angle
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How it works
Area = ½ × r² × θ (θ in radians); arc = r × θ
A sector is a pie slice of a circle. Converting the central angle to radians lets you scale the full circle’s area and circumference down to the slice.
Worked example
A 90° sector of radius 5 has area ½·25·(π/2) ≈ 19.63 and arc 5·(π/2) ≈ 7.85.
Frequently asked questions
What fraction of the circle is it?
The angle ÷ 360. A 90° sector is one quarter of the whole circle.
Difference between arc and chord?
The arc is the curved edge; the chord is the straight line joining the two endpoints.
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Get a circle’s diameter, circumference and area from its radius in one step.
Arc Length Calculator
Find the arc length of a circle from the radius or diameter and the central angle (degrees, radians or gradians) — or from the chord, the arc height, the sector area or the arc itself. Also gives the exact π form, sector and segment area, chord, sagitta, perimeter and worked steps.
This calculator is for educational purposes. Double-check important results before acting on them.