How to Calculate Sector Area
What is Sector Area?
A sector is the "pie slice" region of a circle bounded by two radii and an arc. The sector area calculator finds the area and arc length from the radius and central angle.
Formula
A = (θ/360°) × πr² (degrees) or A = ½r²θ (radians)
- r
- radius (length)
- θ
- central angle (degrees or radians)
- A
- sector area (length²)
Step-by-Step Guide
- 1Sector area = ½r²θ (θ in radians)
- 2Sector area = (θ/360) × πr² (θ in degrees)
- 3Arc length = rθ (radians)
- 4Perimeter of sector = 2r + arc length
Worked Examples
Input
r = 5, θ = 90°
Result
Area = ¼π×25 ≈ 19.63
Input
r = 10, θ = 60°
Result
Area = ⅙π×100 ≈ 52.36
Frequently Asked Questions
What is the difference between a sector and a segment?
A sector is the "pie slice" from two radii; a segment is the region between a chord and the arc.
What angle gives a quarter circle?
A quarter circle (quadrant) has a central angle of 90° or π/2 radians.
How do I find the perimeter of a sector?
Perimeter = 2r + arc length = 2r + rθ (in radians).
Ready to calculate? Try the free Sector Area Calculator
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