The Lesson
The area of a circle is found using the formula:

How to Find the Area of a Circle
Finding the area of a circle is easy.Question
What is the area of a circle with a radius of 5 cm, as shown below?
Step-by-Step:
2
Substitute the radius into the formula. In our example, r = 5.
Area = π × 52 = π × 5 × 5 = 78.5 cm2
Answer:
The area of the circle with a radius of 5 cm is 78.5 cm2."Find the Area" Widget


How to Find the Area of a Circle Using the Diameter
The area of a circle can be found using the diameter rather than the radius. The area of a circle, using the diameter, is found using the formula:

What Is a Circle?
A circle is a shape containing a set of points that are all the same distance from a given point, its center.Radius and Diameter
The diameter of a circle is twice the length of its radius. If you are given the diameter of a circle, halve it to find the radius and put this in the formula. Alternatively, use the formula containing diameter.What Is Pi?
π is the symbol for pi. π is how many times longer a circle's circumference is than its diameter. It is the circumference divided by the diameter: