Circumference calculation Explained

Understanding what a circumference of a circle is and also how to calculation it is crucial as you move to higher level math. In this write-up you will find out the answers come the complying with questions.

You are watching: What is the circumference of a circle with a diameter of 4

What is the circumference of a circle?How have the right to you calculation the one of a circle?

What is the one of a circle?

The circumference the a circle is the distance around the external of the circle. That is choose the perimeter of other shapes prefer squares. You deserve to think the it together the line that specifies the shape. For forms made of straight edges this line is dubbed the perimeter yet for circles this specifying line is called the circumference.

This diagram reflects the circumference of a circle.


There are two various other important ranges on a circle, the radius (r) and the diameter (d). The radius, the diameter, and the circumference are the 3 defining elements of every circle. Provided the radius or diameter and also pi you have the right to calculate the circumference. The diameter is the distance from one side of the circle to the other at its widest points. The diameter will constantly pass with the facility of the circle. The radius is half of this distance. Friend can also think the the radius as the distance between the facility of the circle and also its edge.

This diagram mirrors the circumference, diameter, center, and radius top top a circle.


How can you calculation the circumference of a circle?

If you understand the diameter or radius the a circle, you have the right to work the end the circumference. To begin with, remember that pi is an irrational number written with the prize π. π is around equal to 3.14.

The formula for functioning out the one of a one is:

Circumference of one = π x Diameter the circle

This is frequently written together C = πd. This tells united state that the one of the circle is three “and a bit” times as long as the diameter. We can see this top top the graphics below:


You can also work the end the one of a one if you understand its radius. Remember that the diameter is double the length of the radius. We already know that C = πd. If r is the radius the the circle, climate d = 2r. So, C = 2πr.

Example 1

If a circle has actually a diameter of 10cm, what is that is circumference?


We know that C = πd. Due to the fact that the diameter is 10cm, we recognize that C = π x 10cm = 31.42cm (to 2 decimal places).


Example 2

If a circle has a radius that 3m, what is that circumference?


We understand that C = 2πr. Since the radius is 3m, we know that C = π x 6m = C= 18.84m (to 2 decimal places).

Example 3

Find the lacking length (marked through a ?) on the diagram below:



The missing length is the circumference. Making use of the expertise that the diameter is 4.3m on the diagram and knowing that C = πd, we have the right to calculate the circumference. V a small thinking we can conveniently figure out that, C = π x 4.3m = 13.51m (to 2 decimal places). The lacking length is 13.51m.

How to calculate the circumference of the Earth

Have you ever wondered how large the planet is? Well, using pi it’s possible to work out the one of the Earth! researchers have discovered that the diameter that the planet is 12,742km. Given this information, what is the one of the Earth? get out a item of document and a calculator and also see if you deserve to work it the end on your own.

See more: What To Feed Baby Leopard Geckos Eat? Best Food List, Diet & Feeding

Again, we recognize that C = πd, and that the diameter of the planet is 12,742km. Using this information we have the right to calculate the one of the planet as C = π x 12,742km = 40,030km.

Formula because that the Circumference and also Area of a Circle

mometrixNeed a one calculator? Click the link in ours bio! ##pi ##circumference ##math ##mathematics ##mometrix

♬ original sound – Mometrix test Preparation