Use this Percentage Change Calculator to find the percent increase or decrease between two values. It is useful for prices, grades, finance, analytics, business reports, and any situation where you need to compare an original value with a new value.

Reviewed by: AjaxCalculators Editorial Team
Last updated: April 23, 2026
Method source: Standard percent increase and percent decrease relationships using change relative to the original value
Editorial standards: AjaxCalculators Editorial Policy

What This Percentage Change Calculator Calculates

This calculator can solve for any missing value when at least two are known:

• Original value
• New value
• Percentage change

It also shows:

• Absolute change
• Interpretation as an increase or decrease

How the Percentage Change Calculator Works

Percentage change compares the difference between two values relative to the original value.

Absolute change = new value − original value

Percentage change = (new value − original value) ÷ original value × 100%

This means:

• if the result is positive, it is a percentage increase
• if the result is negative, it is a percentage decrease

You can also rearrange the same relationship to solve for the missing original value or missing new value when the percentage change is already known.

Assumptions and Important Notes

• This calculator uses the standard school and business definition of percentage change relative to the original value.
• A positive result means increase. A negative result means decrease.
• If the original value is 0, ordinary percentage change is undefined because division by zero is not allowed.
• If the original value is negative, the percentage-change interpretation can become less intuitive, so extra caution is needed.
• The absolute change and percentage change describe different things: one is the raw difference, the other is the difference scaled to the original value.

Worked Examples

Example 1: Percentage Increase

Suppose a value increases from 80 to 100.

Step 1: Find the absolute change
100 − 80 = 20

Step 2: Divide by the original value
20 ÷ 80 = 0.25

Step 3: Convert to a percent
0.25 × 100 = 25%

So the percentage change is a 25% increase.

Example 2: Percentage Decrease

Suppose a value decreases from 150 to 120.

Step 1: Find the absolute change
120 − 150 = −30

Step 2: Divide by the original value
−30 ÷ 150 = −0.20

Step 3: Convert to a percent
−0.20 × 100 = −20%

So the percentage change is a 20% decrease.

Example 3: Find the New Value from Percentage Change

Suppose the original value is 200 and the percentage change is +15%.

Step 1: Convert the percent to a decimal
15% = 0.15

Step 2: Find the change amount
0.15 × 200 = 30

Step 3: Add it to the original value
200 + 30 = 230

So the new value is 230.

How to Use This Percentage Change Calculator

1. Enter any two of the three main values: original value, new value, or percentage change.
2. Leave the unknown field blank.
3. Click Calculate to solve the missing value.
4. Review the absolute change and whether the result is an increase or decrease.

How to Interpret the Result

Absolute change tells you the raw difference between the new and original values.

Percentage change tells you how large that difference is relative to the original value.

A percentage increase means the new value is higher than the original value. A percentage decrease means the new value is lower.

If the absolute change is small but the original value is also small, the percentage change can still be large. That is why percent change often looks more dramatic than the raw difference alone.

Practical Uses of a Percentage Change Calculator

• compare old and new prices
• measure revenue or traffic growth
• track decreases in costs or expenses
• analyze score changes over time
• solve missing-value percent problems in school or business math

References

1. OpenStax Prealgebra 2e – percent increase and percent decrease as a percent of the original amount
2. OpenStax Elementary Algebra 2e – solve percent applications
3. AjaxCalculators live Percentage Change Calculator

Related Calculators

• Percentage Calculator
• Percentage Decrease Calculator
• Average Percentage Calculator
• Percentage of a Percentage Calculator
• Fraction to Percentage Calculator

Disclaimer: This calculator is for educational and general calculation use. Percentage change is based on the original value, so results can be undefined or less intuitive when the original value is zero or negative.