Annulus Area Calculator (A = π(R²−r²))
This calculator computes the annulus area: exact formula A = π(R²−r²), worked example R = 8 cm, r = 5 cm → A = 122.52 cm².
- Free, instant, any units.
Figures are estimates from this calculator’s standard formula — adjust the inputs in the tool below for your exact number.
How the annulus area Calculator Works
The calculator applies the exact formula A = π(R² − r²). Worked example: R = 8 cm, r = 5 cm → A = 122.52 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
Enter the measurements
Type the values required by the formula for annulus area.
- 2
Check the units
One unit system throughout — cm, m, ft or in.
- 3
Read the result
The calculator substitutes, evaluates and rounds only at the end.
Use Cases
Floor, plot and panel measurements
School geometry and land surveying
Double-checking material orders and quotes
Tips
- 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
Common Mistakes
Unit mix-ups between cm² and m² (factor 10,000)
Using a slanted length as a perpendicular height
Treating an irregular shape as regular
FAQs
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