Circle calculator
Find a circle’s dimensions from its radius, diameter, circumference or area.
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USDTHE NUMBERS, MADE CLEARInstant calculation
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Check your inputs and select Calculate.
Use one consistent length unit; area uses its square. For example, centimetres give square centimetres. Applies to plane circles only.
Common uses
Find a circle’s dimensions from its radius, diameter, circumference or area.
BEHIND THE NUMBERSFormula & assumptions
d = 2r; C = 2πr; A = πr²
Use one consistent length unit; area uses its square. For example, centimetres give square centimetres. Applies to plane circles only.