Quick guide
How to use this calculator
- Enter values using the notation shown beside each field.
- Choose a calculation mode when the tool offers more than one interpretation.
- Read the primary answer first, then inspect the supporting details.
Calculation method
Apply the stated definition
A = π(R²−r²)
The calculator validates the mathematical domain before returning a result and does not replace undefined states with zero.
Worked example
Worked example
Enter the example values shown in the fields to verify the stated relationship.
A = π(R²−r²)
Supported inputs
Precision and limits
Finite, bounded input
Numeric inputs use finite JavaScript floating-point values with magnitude limits. Results are normally displayed to 12 significant digits; outputs labelled approximate are not exact identities.
Notation
Lengths are unit-neutral but must use one consistent unit throughout a calculation. Angles are entered in degrees where labelled.