A percentage change calculator makes it easy to measure how much a value has increased or decreased compared with its original amount. Instead of working through the formula manually, enter the original value and the new value and the calculator will show the percentage change, the absolute difference, and whether the result represents an increase, decrease, or no change.
Percentage change is useful whenever two values represent the same thing at different points in time. A business might compare this year's revenue with last year's revenue, an investor might measure how much an investment price has changed, a shopper might compare an old price with a new price, or a student might measure improvement between two test scores. It is also widely used in statistics, research, economics, reporting, and data analysis.
This page combines several related tools in one place. In addition to the main percent change calculator, you can calculate percentage increase, percentage decrease, percentage difference between two numbers, increase a number by a selected percentage, or reduce a number by a selected percentage. Choose the appropriate tab above and enter your values.
What Is Percentage Change?
Percentage change expresses the difference between an original value and a new value as a percentage of the original value. It answers a practical question: How large is the change compared with where the value started?
First, subtract the original value from the new value. Next, divide that difference by the original value. Finally, multiply the result by 100 to convert the decimal into a percentage.
- A positive change normally represents an increase.
- A negative change normally represents a decrease.
- A difference of zero means there has been no change.
For example, if a product price changes from 100 to 120, the difference is 20. Dividing 20 by the original value of 100 gives 0.20. Multiplying by 100 gives a 20% increase.
How to Use the Percentage Change Calculator
- Choose Percentage Change from the calculator tabs.
- Enter the Original Value.
- Enter the New Value.
- Click Calculate or press Enter.
- Review the percentage change, difference, and increase or decrease label.
The other tabs allow you to solve closely related percentage problems without needing a separate calculator. Use Percentage Increase when you specifically expect growth, Percentage Decrease when you expect a reduction, and Percentage Difference when neither number should be treated as the starting value. The Increase by % and Decrease by % modes calculate a new value after applying a specified percentage.
Percentage Change Formula
The percentage change formula uses the original number as the base. This is important because the same numerical difference can represent very different percentage changes depending on the starting value.
Example: Original value = 200 and new value = 250.
Difference = 250 − 200 = 50
Percentage change = (50 ÷ 200) × 100 = 25%
Result: 25% Increase
Notice that the division uses 200, not 250. The original value is the reference point from which the change occurred. Dividing by the new value is one of the most common mistakes when people calculate percentage change manually.
Percentage Increase Formula
A percentage increase measures how much a number has grown relative to its starting value. This is useful for measuring sales growth, increases in prices, higher test scores, investment gains, population growth, or changes in any other measurable quantity.
Example: Original value = 80 and new value = 100.
Increase = 100 − 80 = 20
Percentage increase = (20 ÷ 80) × 100 = 25%
Result: 25% Increase
If you use the percentage increase calculator but enter a new value that is lower than the original value, the calculator will tell you that the result is actually a percentage decrease. This helps prevent a change in the wrong direction from being incorrectly described as an increase.
Percentage Decrease Formula
Percentage decrease measures how much a value has fallen relative to its original amount. It is commonly used for discounts, falling prices, reductions in expenses, declining sales, weight changes, inventory reductions, and many other comparisons.
Example: Original value = 200 and new value = 150.
Decrease = 200 − 150 = 50
Percentage decrease = (50 ÷ 200) × 100 = 25%
Result: 25% Decrease
If the new number is higher than the original number, the percentage decrease calculator identifies the change as an increase instead. This is useful when checking data because it immediately shows whether the entered values match the expected direction.
Percentage Difference Formula
Percentage difference is related to percentage change, but the two calculations are not interchangeable. Percentage change requires a clear starting or original value. Percentage difference is intended for comparing two values when neither one should be treated as the base.
The absolute difference between the two values is divided by their average. Because the comparison is centered on both values rather than one original value, percentage difference is useful when comparing measurements, experimental results, estimates, observations, or similar data.
For example, if two measurements are 100 and 110, their absolute difference is 10 and their average is 105. The percentage difference is approximately 9.52%.
Percentage Change Examples
The following examples show how the same formula works for both increases and decreases.
| Original Value | New Value | Percentage Change |
|---|---|---|
| 100 | 120 | 20% Increase |
| 100 | 80 | 20% Decrease |
| 50 | 75 | 50% Increase |
| 200 | 150 | 25% Decrease |
| 80 | 100 | 25% Increase |
| 500 | 450 | 10% Decrease |
| 40 | 60 | 50% Increase |
| 250 | 300 | 20% Increase |
Where Is Percentage Change Used?
Percentage change appears in everyday decisions as well as professional reporting. Because percentages standardize changes relative to a starting value, they make comparisons easier to understand.
Business
- Revenue growth
- Sales changes
- Customer growth
- Expense changes
- Profit comparisons
Finance
- Investment performance
- Stock price changes
- Savings growth
- Financial comparisons
- Changes in account balances
Shopping
- Price increases
- Price decreases
- Discount comparisons
- Old versus new prices
- Checking sale offers
Education
- Test score improvement
- Grade comparisons
- Performance changes
- Research assignments
- Classroom statistics
Statistics & Data Analysis
- Year-over-year change
- Survey results
- Population changes
- Measured values
- Trend analysis
Percentage Change vs Percentage Difference
Choosing the correct formula depends on the relationship between the two numbers. If one value represents a starting point and the other represents a later value, use percentage change. If you are simply comparing two measurements of equal importance, percentage difference is usually more appropriate.
Percentage Change
Use percentage change when one number is clearly the original or base value and the second number is the new value.
Example: Sales rise from $100,000 to $120,000. The percentage change is a 20% increase.
Percentage Difference
Use percentage difference when neither value is considered the original and you simply want to compare two numbers.
Example: Two measurements are 100 and 110. Neither measurement needs to be treated as the starting value.
Common Percentage Calculation Mistakes
Percentage formulas are straightforward once the correct base number is identified, but several common errors can produce misleading results.
- Dividing by the new number: Percentage change normally uses the original number as the denominator.
- Confusing percentage change with percentage difference: Percentage difference treats the two values symmetrically, while percentage change uses a starting value.
- Forgetting to multiply by 100: A decimal such as 0.25 represents 25%, not 0.25%.
- Calling a decrease an increase: Always check whether the new value is higher or lower than the original value.
- Calculating change from zero: Standard percentage change cannot use zero as the original value because division by zero is undefined.
- Confusing percentage points with percentage change: A rate moving from 20% to 25% rises by 5 percentage points, but the relative percentage increase is 25%.