This calculator finds a circle's radius, diameter, circumference, and area when you know one measurement.
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Enter the known radius, diameter, circumference, or area, then calculate the remaining properties. Keep the input unit in mind because lengths use that unit and area uses its square.
Diameter = 2 × radius. Circumference = 2 × pi × radius, or pi × diameter. Area = pi × radius².
A circular table with a diameter of 4 feet has a radius of 2 feet. Its circumference is pi × 4, about 12.57 feet, and its area is pi × 2², about 12.57 square feet.
Yes. Divide the diameter by 2 to get the radius, or multiply the radius by 2 to get the diameter.
That can happen for certain radii, including a radius of 2. The units remain different, so 12.57 feet of circumference is not the same quantity as 12.57 square feet of area.
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