Circular Ring Sector Calculator (A = θ(R²−r²)/2)

The calculator applies the exact formula A = (θ/2)·(R² − r²), θ in radians. Worked example: R = 8, r = 5 cm, θ = π/2 → A = 30.63 cm². Keep every input in one unit system and the result follows in square units (m², ft², cm²); full precision is kept until the final rounding. All side lengths must share one unit or the area comes out scaled wrongly.

1. 1

   Enter the measurements

   Type the values required by the formula for circular ring sector.

2. 2

   Check the units

   One unit system throughout — cm, m, ft or in.

3. 3

   Read the result

   The calculator substitutes, evaluates and rounds only at the end.

• 1

  Area scales with the square of linear dimensions

• 2

  1 m² = 10.764 ft² for quick conversion

• 3

  Sketch and label the shape before entering values

• Unit mix-ups between cm² and m² (factor 10,000)

• Using a slanted length as a perpendicular height

• Treating an irregular shape as regular