Math
Arc Length Calculator
Use this arc length calculator to find the curved distance around part of a circle.
Arc length
—
- Full circumference
- —
- Angle in radians
- —
Student quick launch
Grade planning, algebra checks, and formulas students reach for most.
Study path
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What the arc length calculator solves
Use this arc length calculator to find the curved distance around part of a circle.
Formula
How to use it
- Enter radius.
- Enter central angle in degrees.
- The calculator converts degrees to radians before multiplying.
How to read the answer
Arc length grows with both radius and central angle.
Common mistakes and edge cases
- The formula s = r theta needs radians.
- Do not use diameter as radius.
- Arc length is not sector area.
Worked examples
Sixty-degree arc
Arc length
8.3776
Half circle
Arc length
15.708
Frequently asked questions
Why convert to radians?+
The simple arc length formula s = r theta works when theta is in radians.
What is the arc of a full circle?+
At 360 degrees, the arc length equals the circumference.
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Last updated: May 15, 2026