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Perimeter of a Sector Calculator.

Calculate arc length and perimeter of a circular sector.

On-device calculationNo signup
01

Set your values

Results update as you type.

Arc length: 7.853982

Arc length

0.000000
Perimeter: 17.853982

Perimeter

0.000000

Results update automatically as you type.

Use Cases

Geometry homework and exams

Quickly verify arc length and perimeter calculations for sector problems in math classes.

Example: Find the perimeter of a sector with radius 5 cm and angle 60°.

Design and construction planning

Determine the outer edge length of a sector-shaped piece for cutting materials or laying out curved structures.

Example: Calculate the perimeter of a 90° sector with radius 2 meters for a garden path.

Frequently Asked Questions

How do I calculate the perimeter of a sector?
Enter the radius and the angle (in degrees or radians) into the calculator. It computes the arc length using the formula (angle/360) * 2πr for degrees, then adds twice the radius to get the perimeter.
What units should I use for the radius and angle?
Use any unit for radius (e.g., cm, m, inches) and the angle in degrees or radians as supported by the calculator. The perimeter will be in the same unit as the radius.
Can I use this calculator for a full circle?
Yes, if you set the angle to 360 degrees (or 2π radians), the arc length becomes the circumference, and the perimeter becomes 2πr + 2r, which is the perimeter of a full circle.

Tips & Common Mistakes

Tips

  • Ensure the angle is in the correct unit (degrees or radians) as expected by the calculator to avoid errors.
  • Double-check that the radius and angle correspond to the same sector; a common mistake is using the diameter instead of the radius.
  • For a quick estimate, remember that the arc length is proportional to the angle: a 180° sector has half the circumference.

Common Mistakes to Avoid

  • Using the diameter instead of the radius when entering the radius field.
  • Forgetting to convert the angle to the unit the calculator expects (e.g., entering degrees when radians are required).
  • Confusing the perimeter with the arc length; the perimeter includes the two straight edges (2r).

Last updated: August 13, 2026