Circle Perimeter and Area
Calculate circle circumference and area from radius or diameter.
Perimeter
31,42
Area
78,54
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Formula
C = 2πr, A = πr²
Example: r = 5 → C = 31.42, A = 78.54
Methodology
Circumference O = 2πr, area S = πr². From diameter d: r = d/2.
Example
Radius 7 cm: O ≈ 43.98 cm, S ≈ 153.94 cm².