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.