The LessonThe area of a circle is found using the formula:
In this formula, r is the radius of the circle. The image below shows what we mean by radius:
How to Find the Area of a CircleFinding the area of a circle is easy.
QuestionWhat is the area of a circle with a radius of 5 cm, as shown below?
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
- Click on the shape you're learning about.
- Click on the pad to start.
- Follow the instructions in the bottom-left corner.
- On the last click, the formula, workings, and answer will appear in the yellow box.
- Good luck!
Lesson SlidesThe slider below shows another real example of how to find the area of a circle. Open the slider in a new tab
How to Find the Area of a Circle Using the DiameterThe 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:
In the formula, d is the diameter of the circle. The image below shows what we mean by diameter:
Read more about how to find the area of a circle using the diameter
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 DiameterThe 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:
π is the same for all circles, and is approximately equal to 3.14.