Circle sector calculator
Enter the radius and the central angle and get the area of the sector, together with the arc length and the perimeter of the sector.
Fill in the fields; the answer appears here straight away.
How it's worked out
How it works
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Enter the values
Type the numbers or the formula. Decimals may use a point or a comma. No idea? Click Fill in an example.
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Instant answer
The answer appears as you type, with the most important intermediate values.
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See the working
Under "How it's worked out" you see the steps, handy for checking your own calculation.
The formula
A sector is a fraction of the whole circle, whose area is πr². So sector area = (angle ÷ 360°) × πr², or ½r²θ with the angle θ in radians.
For a radius of 10 and an angle of 60°: (60 ÷ 360) × π × 10² = 52.36.
Perimeter of the sector
The edge of a sector is the arc plus two radii: (angle ÷ 360°) × 2πr + 2r. Only need the curved part? Use the arc length calculator.
Frequently asked questions
Is the circle sector calculator free?
Yes. The circle sector calculator is completely free, with no account, sign-up or usage limit.
How accurate is the result?
The tool calculates with your browser's number precision. For important calculations, always double-check what you entered.
Does it work on my phone?
Yes. The tool works in any modern browser on a phone, tablet or computer.