Enter a circle's radius to calculate its diameter, circumference and area.
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Diameter is simply twice the radius. Circumference is calculated as 2π × radius, the distance around the circle. Area is calculated as π × radius², the amount of space enclosed by the circle. All three use π (pi), approximately 3.14159.
Divide the diameter by 2 to get the radius, then enter that value.
Rearrange the formula to solve for radius first: radius = circumference ÷ (2π), or radius = √(area ÷ π), then enter that radius here.
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