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Arc length calculator

Arc length = radius × central angle in radians. Sector area = radius² × angle in radians ÷ 2.

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Arc length calculator processes your input in this browser. Inputs and results are excluded from analytics. Recent tools save tool names, visit counts and last-visit times. Saved tools store only their names. Draft saving is optional and stays on this device; delete saved text with the draft controls. Loading text from a URL is optional and contacts that server; its URL and your IP address are visible to the server. An optional “Use in” action keeps a handoff in this tab. The next tool removes it on arrival and ignores it if more than a minute has passed.

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Answer

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Arc length = radius × central angle in radians. Sector area = radius² × angle in radians ÷ 2.

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Precision and calculation record
Rounding changes displayed numbers, not the calculation. Text, fractions, matrices and CSV schedules keep their own formatting. Automatic keeps up to 12 significant digits, with money shown to cents where applicable.
Step-by-step calculation
Inputs are substituted below. Each line evaluates the next operation; intermediate values are displayed to 12 significant digits while the calculation uses full precision.
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    Save the current answer, then change an input to compare. This clears when you leave.
    Formula and assumptions
    The angle is measured at the circle center. Use degrees from 0 to 360; arc length uses the radius unit.
    Automatic precision shows numbers to 12 significant digits. Thousands separators such as 1,000 are accepted; use a dot for decimals.
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    Updated 
    Using Arc length calculator
    Arc length = radius × central angle in radians. Sector area = radius² × angle in radians ÷ 2.
    The angle is measured at the circle center. Use degrees from 0 to 360; arc length uses the radius unit.
    Next: Ellipse calculator
    A worked example
    With radius = 3, central angle (degrees) = 60, the arc length is 3.141592653589793.
    Next: Segment area calculator
    Before you use the result
    The angle is measured at the circle center. Use degrees from 0 to 360; arc length uses the radius unit.
    Example results for radius
    These examples use Central angle (degrees): 60. They are reference calculations, not recommended settings.
    RadiusArc length
    1.51.57079632679
    33.14159265359
    66.28318530718
    Cite this page
    ToolOctopus. “Arc length calculator.” Updated 2026-09-26. https://tooloctopus.com/arc-length-calculator.
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