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Find the Radius of a Circle

Simple instructions for finding the radius of a circle if the diameter is known.

find the radius

Find the radius of a circle using these simple instructions.


The radius of a circle is the distance from the center point to any point on the circle's perimeter. You use the term radii when referring to more than one radius. If you decided to draw two radii at opposite sides, then you would have made a line traverse the entire circle like the example illustrates.


If you know the diameter of the circle then you simply divide the diameter by 2 in order to get the radius.

See also: Find diameter and circumference of a circle | Formula for finding the area of a rectangle | What is a circle? | What is the radius of a circle? | What is the diameter of a circle? | What is the circumference of a circle?