Sector Area Calculator
Enter the circle radius and the sector angle — you get the sector area, the arc length, and what percent of the full circle it is. Angle can be in degrees or radians.
Enter values — the result will show live here.
How to use
- Enter the circle radius and the sector angle, then choose degrees or radians.
- Read the sector area, arc length and the percent share of the full circle.
- Change the angle to see how the share of the circle grows or shrinks.
Note: Formulas: Sector area = (theta/360) x pi r² (degrees) or (1/2) r² theta (radians). Arc length = r x theta (radians). The full circle area is also shown for comparison.
Tips
- A 90-degree sector is exactly one quarter of the circle.
- Arc length is the same fraction of the full circumference.
- Radians and degrees give the same answer — pick whichever the question uses.
Frequently Asked Questions (FAQ)
What do I enter to find the sector area?
Enter the circle radius and the sector angle, then choose degrees or radians as the angle unit.
What results does it show?
It shows the sector area, the arc length, and what percent of the full circle the sector is.
Which formulas does it use?
For degrees it uses (theta/360) x pi r squared, and for radians it uses (1/2) r squared theta.
Do the results update as I type?
Yes. Enter values and the result shows live with no button needed.