Annulus Area 計算機

An annulus is a ring-shaped region between two concentric circles. The area calculation subtracts the inner circle from the outer circle, useful in engineering and architecture.

Enter the outer radius R Then: Enter the inner radius r Then: Calculate π(R² - r²).

Example: Input R = 10 cm, r = 6 cm gives a result of Area ≈ 201 cm² (π(100 - 36) ≈ 201).

Yes — completely free with no registration, download, or subscription required. All calculations happen instantly in your browser.

Our Annulus Area 計算機 uses verified mathematical formulas and is accurate to multiple decimal places. Results are calculated in real-time using the same methods used by professionals.