Calculator A to Z

Choose the formula matching the variables you have, select each input/output unit and enter the values. Calculator A to Z shows the formula and converts inputs to base units before evaluating and converting the result. Its circle-area-from-diameter page uses A = πD²/4, with diameter as a length and area as a squared unit; the result can be copied and the steps inspected. Radius, circumference and chord-based routes are separate alternatives, so selecting the correct geometric quantity matters. The site describes the online calculator as free and offers formula PDF collections. These formulas describe their stated models rather than checking whether a real object meets the assumptions.