Circle Area Calculator

The area of a circle is calculated using the formula 'pi times r squared' (A = πr²). The circumference is '2πr' and the diameter is '2r.' This tool lets you enter any single measurement — radius, diameter, or circumference — and automatically calculates all other values including the area.

For example, if you only know the diameter, entering it will compute the radius, area, and circumference simultaneously. You can also input the circumference to find the area, which is useful when working with physical measurements.

This calculator supports multiple units: millimeters (mm), centimeters (cm), and meters (m), allowing flexibility for precision engineering to everyday calculations. Adjust decimal precision from 2 to 8 places based on your needs. The formula used for each calculation is always displayed, making it an excellent educational tool for learning circle geometry.

Real-time calculation updates results as you type, and a one-click copy feature lets you easily transfer values. Ideal for mathematics education, engineering and architectural design calculations, and general-purpose circle measurements.