Arc Length Calculator
Find the arc length of a circle from its radius and central angle in degrees or radians free in your browser with this quick arc length calculator.
Enter Values
Shape
Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.
How to use this calculator
- Enter the radius and angle.
- Press Calculate.
How it works
Arc length = (angle ÷ 360) × 2 × π × radius.
Worked example
radius 2 m, 90°. ≈ 3.14 m.
Common mistakes
- Using the wrong angle unit — degrees use angle/360, radians use radius × angle.
- Confusing arc length (along the curve) with chord length (straight across).
Frequently asked questions
How do I calculate arc length?
Arc length = (angle ÷ 360) × 2πr for degrees, or radius × angle for radians — the portion of the circumference the arc spans.
How is arc length different from chord length?
Arc length follows the curve; the chord is the straight line between the arc's endpoints, and is always shorter.
Can I enter the angle in radians?
This tool uses degrees (the angle as a fraction of 360°). Convert radians to degrees first — multiply by 180 ÷ π.
Related tools
- Sector Area Calculator
- Circumference Calculator
- Circle from Diameter Calculator
- Annulus Area Calculator
- Circle Area Calculator
- Cone Surface Area Calculator
Explore more in Geometry, Shape, Area & Volume.
Cite this tool
Zerdly. (2026). Arc Length Calculator. Retrieved from https://www.zerdly.com/tools/arc-length-calculator/
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.