To calculate the diameter of a circle we use the formula D = 2r. The diameter of any circle is the longest chord of the circle, that passes through the centre of the circle. The diameter of any circle is found using various methods that are covered in this article.

In this article, we will explore the diameter of the centre definition, how to find the diameter of a circle along with the basics of the diameter of the circle. We will also discuss different formulas for calculating the diameter of a circle and also solve some examples.

What is Diameter of a Circle?

Diameter of a circle is the largest chord of the circle passing through the centre of the circle. In other words, the line from one point on the circle to another point passing through the center of the circle is called as diameter of the circle. The below diagram represents the diameter of the circle.

How to Find Diameter of a Circle?

Diameter of a circle is easily calculated using the steps added below if its radius is given,

Step 1: Note the radius of the given circle.

Step 2: Use the formula, Diameter = 2 × Radius, i.e., d = 2 × r

Step 3: Put the value of the given parameter in the suitable formula and simplify the same to get the required answer.

Example: Find diameter of a circle with radius of 15 units.

Given,

Radius of Circle = 15 units

Diameter of Circle = 2 × Radius

D = 2 × 15 = 30 units

Thus, diameter of circle is 30 units.

How to Calculate Diameter of a Circle

Below are different ways for calculating diameter of circle.

• Diameter when Radius is Given
• Diameter when Circumference of a Circle is Given
• Diameter when Area of Circle is Given

Diameter when Radius is Given

We know that diameter of circle is sum of two radii of circle. In other words, diameter of circle is two times the radius of the circle. So, to calculate the diameter of circle we use the below formula.

Diameter of Circle = 2 × Radius of Circle

D = 2 × r

where,

• D is Diameter of Circle
• R is Radius of Circle

Diameter when Circumference of a Circle is Given

Circumference of a Circle is equal to 2πr. To calculate the diameter of circle we replace 2r by D as D = 2r. So, the circumference of circle in terms of diameter is given by:

Circumference of Circle(C) = πD

D = C/π

where

• C is Circumference of Circle
• D is Diameter of Circle

Diameter when Area of Circle is Given

Area of a circle is equal to πr². To calculate the diameter of circle we replace r by D/2 as D = 2r. So, the area of circle in terms of diameter is given by:

Area of Circle(A) = π×(D/2)²

D = 2√(A/π)

where,

• A is Area of Circle
• D is Diameter of Circle

Examples of Diameter of a Circle

Example 1: Find the diameter of the circle if the radius of circle is 12 units.

Solution:

To calculate diameter, we use the formula:

Diameter = 2 × Radius of Circle

Diameter = 2 × 12

Diameter = 24 units

So, the diameter of given circle is 24 units.

Example 2: Calculate the diameter of the circle if the area of circle is 4π unit².

Solution:

To calculate the diameter of the circle we use the following formula.

Area of Circle = π× (D/2)²

4π = π× (D/2)²

(D/2)² = 4

D² = 16

D = 4 units

Thus, diameter of circle is 4 units.

Example 3: If the circumference of circle is 52 then, calculate the diameter of the circle.

Solution:

To calculate the diameter of the circle we use the following formula.

Circumference of Circle = πD

52 = πD

D = 52 / π

D = 16.55 units

So, diameter of given circle is 16.55 units.

Practice Questions on Diameter of a Circle

Q1: Find the diameter of the circle if the radius of circle is 5 units.

Q2: Find the diameter of the circle if the area of circle is 20 unit².

Q3: If the circumference of circle is 24 then, calculate the diameter of the circle.

FAQs on Diameter of a Circle

How to Find Diameter of Circle?

To find the diameter of circle we use the formula: D = 2r where, r is radius of circle.

How to Find Diameter of a Circle Without the Radius?

To find diameter of circle if the radius of circle is not given, we use formulas of circumference and area of circle.

• Circumference of Circle = πD

• Area of Circle = π× (D/2)²

What is diameter of a 10 inch circle?

Diameter of a 10-inch circle is 10 inches.