Annulus Area Calculator
Annulus Area Calculator finds the area of a ring from its outer radius and inner radius using pi times the difference of the squared radii, returning the area to four decimals.
What this calculator does
The Annulus Area Calculator estimates your result instantly from the values you enter, using standard math & conversions formulas. Annulus Area Calculator finds the area of a ring from its outer radius and inner radius using pi times the difference of the squared radii, returning the area to four decimals. Calculations run in your browser, so nothing you type is sent to a server, and the output is an estimate rather than a certified or official figure.
Result
About Annulus Area Calculator
An annulus is the region between two concentric circles. This calculator takes the outer radius R and inner radius r and returns the ring area as π × (R² − r²).
Inner radius must not exceed the outer radius, so the two circles always describe a valid ring.
Formula & Mathematical Calculation
Area = f(Outer Radius, Inner Radius)
Calculated according to standard math formulas implemented in the calculator core.
Calculation Example
With an outer radius of 8 and an inner radius of 5, the area is π × (8² − 5²) = π × (64 − 25) = π × 39 = 122.522113..., which the calculator rounds to 122.5221.
Key Benefits
- Computes ring area directly from two radii
- Uses the exact pi times (R squared minus r squared) formula
- Validates that the inner radius does not exceed the outer radius
- Rounds the area to four decimal places for clarity
How to Use this Calculator
-
Enter the outer radius
Type the outer radius R into the Outer Radius field. -
Enter the inner radius
Type the inner radius r into the Inner Radius field. -
Calculate
Select Calculate and read the Area result and interpretation.
Assumptions & Limitations
What the calculation assumes
- Every value you enter is treated as an exact, known amount.
- Any rate or interval you enter is assumed to hold for the whole period unless the form asks for it separately.
- Results use standard published formulas and account only for the values entered above.
- Rounding is applied for display; the underlying calculation uses your full precision.
- Results are returned in the same units you enter, unless the tool states the output unit.
What it does not cover
- Annulus Area Calculator produces a calculated result for reference and learning, not a certified or official measurement.
- Real-world outcomes differ when tolerances, rounding rules or local standards apply.
- Definitions and standards vary by region and change over time; verify the convention that applies to your case.
- Figures are only as accurate as the inputs you supply — check them before acting on the result.
- For work where the result carries real consequences, confirm it against an authoritative source.
Frequently Asked Questions
Free to use, no account needed. Calculations run in your browser, so nothing you type is sent to a server. Results are estimates — how we build and check our calculators.