What Is Percentage Change?

Percentage change describes how much a value has changed relative to its original value.

The general formula is:

If the new value is greater than the original value, the result represents an increase. If the new value is lower, it represents a decrease.

How to Calculate Percentage Increase

Percentage increase tells you how much a value has increased compared with where it started.

The important point is that the calculation uses the original value as the reference.

Percentage Increase Example

Suppose a product originally costs $80 and its price increases to $100.

First, find the difference:

Next, divide the increase by the original value:

Finally, multiply by 100:

Therefore, the price increased by 25%.

How to Calculate Percentage Decrease

Percentage decrease shows how much a value has fallen relative to its original value.

Again, the original value is used as the reference point.

Percentage Decrease Example

Suppose a product originally costs $120 and its price falls to $90.

First, calculate the difference:

Divide the decrease by the original price:

Convert the decimal to a percentage:

The price therefore decreased by 25%.

Percentage Increase vs. Percentage Decrease

Although the formulas are similar, the order of subtraction changes depending on whether the value increased or decreased.

In both cases, the original value is the reference used in the calculation.

How to Calculate a Salary Increase

Percentage increase is commonly used to calculate changes in salary.

Suppose your salary increases from $2,000 to $2,300 per month.

The salary increased by 15%.

The same calculation can be used for hourly wages, annual salaries, bonuses and other monetary amounts.

How to Calculate a Discount

Discounts are a common example of percentage decrease.

Suppose an item costs $200 and has a 30% discount.

First, calculate the discount amount:

Then subtract the discount from the original price:

The final price is $140.

You can also use the Atlasaro Percentage Calculator to perform the calculation automatically.

Why a 20% Increase Followed by a 20% Decrease Does Not Return to the Original Value

One of the most common percentage mistakes is assuming that equal percentage increases and decreases cancel each other.

Consider a starting value of 100.

Increase it by 20%:

Now decrease the new value by 20%:

The final result is 96, not 100.

The reason is that the second 20% is calculated from 120, not from the original value of 100.

Percentage Increase and Decrease in Real Life

Percentage changes are used in many situations, including:

• Product price increases and discounts.
• Salary and wage changes.
• Changes in fuel prices.
• Investment gains and losses.
• Business revenue changes.
• Population growth or decline.
• Changes in test scores.
• Changes in website traffic.
• Changes in household expenses.
• Statistical comparisons.

Common Mistakes When Calculating Percentage Change

Most percentage errors happen because the wrong reference value is used or the percentage is interpreted incorrectly.

• Using the new value instead of the original value.
• Forgetting to multiply the decimal result by 100.
• Confusing percentage points with percentage change.
• Assuming equal increases and decreases cancel each other.
• Rounding the numbers too early.
• Applying a discount to an already discounted price without realizing that the second percentage uses a new base.

Percentage Change vs. Percentage Points

These two concepts are often confused.

Suppose an interest rate increases from 5% to 7%.

The direct difference is:

But the relative increase is:

Therefore, the rate increased by 2 percentage points, which corresponds to a 40% relative increase.

Related Atlasaro Guides

Want to learn more about percentage calculations? Read our detailed Percentage Calculator Guide .

You can also learn how to work with dates using our Date Calculator Guide .

For age-related date calculations, see the Age Calculator Guide .