A sector is the region between two radii and an arc. Think of it as a "pie slice" of the circle.

How do I find the area if I know the diameter?

Divide the diameter by 2 to get the radius, then use A = pi × r². Alternatively, A = pi × d²/4.

What is the relationship between arc length and sector area?

Both are proportional to the central angle. Sector area = (1/2) × r × arc length.

Advanced Circle Calculator

Calculate circle area, circumference, diameter, and sector area from the radius. Includes arc length computation.

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Radius

Sector Angle (degrees)

deg

Area

78.5398

Circumference31.4159

Diameter10.0000

Arc Length7.8540

View formula & how it works →

Circle Calculations

Formulas

Area = pi × r²

Circumference = 2 × pi × r

Sector Area = pi × r² × (angle / 360)

Arc Length = 2 × pi × r × (angle / 360)

A sector is a "pie slice" of the circle defined by a central angle.

Example Calculation

A circle with radius 5, find area and a 90-degree sector.

01Area = pi × 25 ≈ 78.5398
02Circumference = 2 × pi × 5 ≈ 31.4159
03Sector area = 78.5398 × 90/360 ≈ 19.6350
04Arc length = 31.4159 × 90/360 ≈ 7.8540

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