Percentage Change Calculator
WebToola
Percentage Change Calculator
Compare an original value with a new value. The change uses the absolute original value as its denominator.
About the Percentage Change Calculator
The Percentage Change Calculator measures how much a value has increased or decreased compared with its original value. Enter the original value and the new value to calculate both the percentage change and the numerical difference between them.
A positive change is shown as an increase, while a negative change is shown as a decrease. This makes it easy to compare changes in prices, measurements, quantities, statistics, business figures and other numerical values.
How to Calculate Percentage Change
Enter the original value followed by the new value. The calculator compares the two and shows the percentage change along with the numerical difference.
For example:
Original value: 100
New value: 125
The result is:
Change: 25% (increase)
Difference: 25
This means the value increased by 25, which represents a 25% increase relative to the original value.
If the new value were 75 instead, the difference would be -25 and the result would represent a 25% decrease.
Percentage Change Formula
Percentage change compares the difference between the new and original values with the magnitude of the original value.
WebToola calculates it as:
Percentage change = ((New value − Original value) ÷ |Original value|) × 100
The vertical bars around the original value mean its absolute value is used as the denominator.
Using an original value of 100 and a new value of 125:
Difference = 125 − 100 = 25
Then:
(25 ÷ |100|) × 100 = 25%
The result is therefore a 25% increase.
Percentage Increase vs. Percentage Decrease
When the new value is greater than the original value, the result represents an increase. When the new value is lower, it represents a decrease.
For example:
100 → 125
Difference: +25
Percentage change: 25% increase
Whereas:
100 → 75
Difference: -25
Percentage change: 25% decrease
The numerical difference tells you how much the value changed, while the percentage change expresses that difference relative to the original value.
Why Does the Calculator Use the Absolute Original Value?
This calculator uses the absolute value of the original number as the denominator. This keeps the denominator positive when comparing values that begin below zero.
For example, when the original value is -100, its absolute value is 100, so the change is measured relative to a magnitude of 100 rather than dividing by -100.
Percentage changes involving negative values can require careful interpretation depending on the context, so it can be useful to consider both the percentage result and the numerical difference shown by the calculator.
Common Uses for Percentage Change
Percentage change is useful whenever you need to compare an old value with a new value. Common examples include changes in prices, revenue, costs, measurements, populations, scores, website statistics and other numerical data.
For general percentage calculations—such as finding 20% of 150 or determining what percentage one number is of another—use WebToola’s Percentage Calculator instead.
Frequently Asked Questions
How do I calculate percentage change?
Subtract the original value from the new value, divide the difference by the absolute value of the original value, and multiply by 100:
((New − Original) ÷ |Original|) × 100
What is the percentage increase from 100 to 125?
The difference is 25. Dividing 25 by 100 and multiplying by 100 gives a 25% increase.
What is the percentage decrease from 100 to 75?
The difference is -25, which represents a 25% decrease relative to the original value of 100.
What is the difference between percentage change and numerical difference?
The numerical difference is calculated by subtracting the original value from the new value. Percentage change expresses that difference relative to the magnitude of the original value.
For example, from 100 to 125, the numerical difference is 25, while the percentage change is 25%.
Can percentage change be greater than 100%?
Yes. If the change is greater than the magnitude of the original value, the percentage change can exceed 100%. For example, increasing from 100 to 250 is an increase of 150, or 150%.
What happens if the original value is zero?
Percentage change is undefined when the original value is zero because calculating percentage change would require division by zero. If you enter 0 as the original value, the calculator will display:
Percentage change is undefined when the original value is zero.
Does WebToola store the values I enter?
No. The Percentage Change Calculator runs in your browser and does not send or save the values you enter.