The radius of a circle can be calculated by measuring the diameter, and then dividing the diameter into half. This is because in theory, the radius of a circle is half of the circle’s diameter. The diameter of the circle can either be found by direct measurement or from other relations in case more variables are given.
For instance if the perimeter of a circle is given, then radius is directly found by the relation Perimeter = 2 x pi x radius. Similarly, if the area is given, then radius can be found by using Area = pi x radius squared.
