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Radius, area and circumference.
The Circle Calculator solves every property of a circle from any single measurement. Enter one of the radius, diameter, circumference or area and it derives the other three instantly.
It works by first recovering the radius from whatever you know, then applying the standard circle formulas. This is handy in geometry, engineering, and any DIY task involving round objects.
It is the distance all the way around the edge, equal to 2πr or π times the diameter.
Divide the area by π and take the square root: r = √(A ÷ π).
Yes. Perimeter is the general term for the boundary length; for a circle it is called the circumference.
π is the fixed ratio between a circle's circumference and its diameter, so it appears in every circle formula.