# What Is a Percentage Change?

## What Is a Percentage Change?

A percentage change is the change from one value to another value, expressed as a percentage.

## A Real Example of a Percentage Change

Imagine that a company sells 100 calculators in a week. The next week the company sells 120 calculators.

The percentage change from 100 to 120 is 20%. ## How to Find a Percentage Change

100 to 120 is a percentage change of 20%. How do we know it is 20%?

• The change from 100 to 120 is the difference between the numbers.

120 − 100 = 20

The change is 20.

• The percentage change expresses the change (20) as a percentage of the original number (100).

20 = 20% of 100

The percentage change is 20%.

Read more about how to find a percentage change

## Other Questions with a Percentage Change

In the example above, we found the percentage change from an old number to a new number.

You need to use percentage changes in other ways:

• You need to be able to find the new number if you are told the old number and the percentage change.

For example, if a \$10 an hour wage increased by 20%, you would have to work out that the new wage would be \$12 an hour. • You need to be able to find the old number if you are told the new number and the percentage change.

For example, if there are 33 students in a class after a 10% increase, you would have to work out that there were originally 30 students in the class. ## Slider

The slider below gives more examples of percentage changes.

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What is a percentage? Understanding percentages ( interactive widget)