Diameter of a Circle: Definition, Formula & Real-World Applications

Learn the diameter of a circle, including its formula, derivation, and practical uses in everyday life, physics, and engineering. Learn how to solve problems step-by-step.

Consider yourself and your friends enjoying a big pizza. Prior to slicing it into equal pieces, you observe that the longest straight line from one side to the other runs through the middle of the pizza. The diameter is that! It is an essential geometric notion that is used in everything from building construction to tire design.

In this article, we'll explore:

• What is the diameter of a circle?
• How is the diameter of a circle calculated?
• Where is the diameter of a circle applied in real life?

Also Check: Centroid of a Triangle

What is the Diameter of a Circle?

Any segment of a straight line that crosses the circle's center and has endpoints on its circumference is considered the circle's diameter. Another name for the diameter is the circle's longest chord.

A circle's diameter is equal to twice its radius in length. The diameter of a circle is measured from one end to a point on the other end that passes through the center, whereas the radius is measured from the circle's center to one endpoint on its perimeter.

Diameter of Circle Formula

The diameter of a circle can be determined using the radius, circumference and area of a circle:

Diameter of a Circle Using Radius

The length of the line segment connecting the circle's center to one of its endpoints is known as the radius (r). The diameter of the circle is twice its radius, whereas the length of the line segment that connects the circle's center to an endpoint is called its radius (r).
Diameter = 2 × radius

Also Check: Collinear Points

Diameter of a Circle Using Circumference

Boundary enclosed by the circle is called its circumference (C). Circumference of a circle is given by
C = πD
Therefore, Diameter of a circle can be calculated from the above formula as follows
D = C / π
Diameter = Circumference / π

Diameter Formula Using Area of Circle

The total amount of space inside a circle's perimeter is its area. Using the formula for the area of a circle, area (A) = π(Radius)², we may calculate the diameter of a circle. When we change the radius to D/2, we obtain
A / π = (D/2)²
D/2 = √(A / π)
D = 2 × √(A / π)
Diameter = 2 × √(Area / π)

Examples to Make It Easy

Example 1: A circle has a radius of 7 cm. What's its diameter?
Solution: Radius of the given circle is 7 cm. Diameter of the circle, when the radius is given, can be calculated using the following formula:
Diameter = 2 × radius
Diameter = 2 × 7 cm = 14 cm
Therefore, the diameter of the given circle is 14 cm.

Example 2: A circular park has a circumference of 31.4 meters. Find its diameter.
Solution: Circumference of the given circle is 31.4 m. Diameter of the circle, when the circumference is given, can be calculated using the following formula:
Diameter = Circumference / π
Diameter = 31.4 / π = 31.4 / 3.14 = 10 m
Therefore, the diameter of the given circular park is 10 m.

Example 3: The area of a circular pond is 78.5 square meters. Find its diameter.
Solution: Area of the given circle is 78.5 sq. m. Diameter of the circle, when the area is given, can be calculated using the following formula:
Diameter = 2 × √(Area / π)
Diameter = 2 × √(78.5 / 3.14) = 2 × √25 = 2 × 5 = 10 m
Therefore, the diameter of the circular pond is 10 m.

Also Check: Concurrent Lines

Practice Questions

Test yourself with these problems:

1. A circular mirror has a radius of 12 cm. Find its diameter.
2. A wheel has a circumference of 62.8 cm. What's its diameter?
3. A circular track covers an area of 314 square meters. Find its diameter.

Where Do We Use This in Real Life?

• Engineering & Construction - Used in bridge design, tunnels, and pipelines.
• Astronomy & Space Science - Helps measure planets and telescope lenses.
• Manufacturing & Design - Determines the size of gears, wheels, and mechanical parts.
• Sports & Recreation - Used in stadium designs and sports equipment.
• Everyday Life - Helps when measuring round tables, mirrors, and decoration.

A circle's circumference is a straightforward yet effective idea that has applications in many facets of life. Knowing dimension makes things easier, whether you're cutting a pizza, measuring something, or developing a product!