How to Calculate and Solve for the Perimeter or Circumference, Radius and Diameter of a Circle | The Calculator Encyclopedia

The image above is a circle.

To compute the perimeter or circumference of a circle, one essential parameter is needed and this parameter is the radius of a circle (r). You can also use the diameter of a circle to compute the area of a circle (d).

The formula for calculating the perimeter or circumference of a circle is:

P = 2πr

Where:

P = Perimeter or Circumference of a circle
r = Radius of a circle

Let’s solve an example:
Find the perimeter or circumference of a circle where the radius of a circle is 8 cm.

This implies that;
r = Radius of a circle = 8 cm

P = 2πr
P = 2 x 3.142 x 8
P = 50.265

Therefore, the perimeter or circumference of a circle is 50.265 cm.

Calculating the Area of a Circle using the Diameter of a Circle.

The formula is P = πd

Where:

P = Perimeter or Circumference of a circle
d = Diameter of a circle

Let’s solve an example:
Find the perimeter or circumference of a circle where the diameter of a circle is 10 cm.

This implies that;
d = Diameter of a circle = 10 cm

P = πd
P = 3.142 x 10
P = 31.42

Therefore, the perimeter or circumference of a circle with diameter is 31.42 cm.

How to Calculate Radius of a Circle when Perimeter or Circumference of the Circle is Given

r = P /

where;

r = Radius of a circle
P = Perimeter or Circumference of a circle

Let’s solve an example:
Find the radius of a circle where the perimeter or circumference of the circle is 16 cm.

This implies that;
P = Perimeter or Circumference of the circle = 16 cm

r = P /
r = 16 / 6.284
r = 2.55

Therefore, the radius of the circle is 2.55 cm.

How to Calculate Diameter of a Circle when Perimeter or Circumference of the Circle is Given

d = P / π

where;

d = Diameter of a circle
P = Perimeter or Circumference of a circle

Let’s solve an example;
Find the diameter of a circle where the perimeter or circumference of the circle is 20 cm

This implies that;
P = Perimeter or Circumference of the circle = 20 cm

d = P / π
d = 20 / π
d = 6.365

Therefore, the diameter of the circle is 6.365 cm.