Arc length calculator
Enter the radius and the central angle and get the length of the arc, with the sector area, the perimeter of the sector and the circumference of the whole circle.
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
The arc is a fraction of the full circumference 2πr: arc length = (angle ÷ 360°) × 2πr. In radians it is even simpler: arc length = r × θ.
For a radius of 10 and an angle of 60°: (60 ÷ 360) × 2π × 10 = 10.47.
Arc, sector and chord
The arc is the curved part of the edge. The sector is the slice between two radii and the arc, like a slice of pizza; its area is in the circle sector calculator. The central angle must be between 0° and 360°.
Frequently asked questions
Is the arc length calculator free?
Yes. The arc length 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.