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%.
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.