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Arc Length Calculator.

Calculate circular arc length from radius and central angle.

On-device calculationNo signup
01

Set your values

Results update as you type.

Arc length: 7.853982 units

Arc length

0.000000units
Angle (rad): 1.570796 rad

Angle (rad)

0.000000rad

Results update automatically as you type.

Use Cases

Geometry homework and math practice

Quickly verify arc length calculations for school assignments or self-study, ensuring accuracy in problems involving circles and sectors.

Example: Find the arc length of a 60° sector in a circle with radius 5 cm.

Engineering and design measurements

Determine the length of curved components in mechanical parts, architectural arches, or manufacturing templates without manual formula work.

Example: Calculate the length of a curved metal strip with radius 2 m and central angle 45°.

Frequently Asked Questions

How do I calculate arc length using this calculator?
Enter the radius of the circle and the central angle in degrees. The calculator uses the formula: arc length = radius × angle in radians. Since the angle is in degrees, it converts it to radians automatically (multiply by π/180).
What units can I use for the radius?
The calculator accepts any unit for the radius (e.g., meters, centimeters, inches). The arc length will be in the same unit as the radius. For example, if you enter radius in meters, the arc length will be in meters.
Can I use this calculator for angles greater than 360°?
Yes, you can enter any positive angle. For angles greater than 360°, the calculator will give the arc length for that angle, which may represent multiple full rotations plus a partial arc. The formula still works correctly.

Tips & Common Mistakes

Tips

  • Ensure the central angle is in degrees, as the calculator expects that unit. If you have radians, convert to degrees first (multiply by 180/π).
  • Double-check that the radius value is positive. Negative radii are not physically meaningful for a circle.
  • For a full circle (360°), the arc length equals the circumference (2πr). Use this as a quick sanity check.
  • If you need the arc length for a sector, remember that the central angle is the angle at the center of the circle, not the angle of the sector's boundary.

Common Mistakes to Avoid

  • Forgetting to convert the angle from degrees to radians manually – this calculator does it for you, but if you use the formula elsewhere, remember to convert.
  • Using the diameter instead of the radius. The calculator asks for radius, so if you have the diameter, divide it by 2 first.
  • Entering the angle in radians but expecting the calculator to treat it as degrees – always check the unit label.

Last updated: August 13, 2026