Cut a slice from a round pizza and you are holding a sector: two radii and the arc between them, the fundamental wedge of circular geometry. Its area is a fixed fraction of the whole circle's area, and that fraction is the central angle over 360° — so A = (θ/360°) × πr². A 60° slice of a radius-5 circle is one-sixth of the pie: (60/360) × π × 25 ≈ 13.09. Enter the Radius and the Central Angle (degrees) and read the Area result. The most common slip is entering the angle in radians while the calculator expects degrees, or vice versa — a 60° angle entered as 60 radians would produce nonsense. Sectors show up in pie charts, windshield wiper coverage, sprinkler spray patterns, and anywhere a rotating arm sweeps an area. As a bonus check, the sector's arc length is (θ/360°) × 2πr, so the same two inputs describe the slice's curved edge too.

With the pre-filled defaults — Radius 5, Central Angle (degrees) 60 — the Area Of Sector Calculator returns Area 13.0900. Change any input and those results update instantly, so you can see exactly how each number you enter moves the answer.