Percent Change Calculator
Enter an original value and a new value to calculate the percent increase or decrease instantly.
What Is Percent Change?
Percent change tells you how much a value has increased or decreased relative to its starting point. It is one of the most useful calculations in finance, business, economics, science, and everyday life because it shows change in a normalized way. Instead of only saying “the value rose by 30,” percent change answers the better question: “30 compared to what?”
For example, a $30 increase on $100 is huge (30%), but a $30 increase on $10,000 is tiny (0.3%). That context is exactly why percent change is so widely used.
Percent Change Calculation Formula
Where:
- Original Value is your starting point (sometimes called old value or initial value).
- New Value is the final amount after change.
- A positive result means an increase.
- A negative result means a decrease.
Quick Example
If a product price goes from 80 to 100:
- Change = 100 − 80 = 20
- Percent Change = (20 ÷ 80) × 100 = 25%
The price increased by 25%.
Step-by-Step Method
- Find the difference: new − original.
- Divide that difference by the original value.
- Multiply by 100 to convert to a percentage.
- Interpret the sign: plus is increase, minus is decrease.
More Worked Examples
1) Percent Increase
Your website traffic rises from 2,000 visits to 2,600 visits.
- Change = 2,600 − 2,000 = 600
- Percent Change = (600 ÷ 2,000) × 100 = 30%
Traffic increased by 30%.
2) Percent Decrease
A stock drops from 50 to 42.
- Change = 42 − 50 = −8
- Percent Change = (−8 ÷ 50) × 100 = −16%
The stock decreased by 16%.
3) Grades Example
A student score improves from 72 to 81.
- Change = 81 − 72 = 9
- Percent Change = (9 ÷ 72) × 100 = 12.5%
The score improved by 12.5%.
Percent Change vs Percentage Points
These two are often confused.
| Situation | Correct Description |
|---|---|
| Interest rate moves from 4% to 6% | Up by 2 percentage points, which is a 50% increase relative to 4% |
| Conversion rate drops from 10% to 8% | Down by 2 percentage points, which is a 20% decrease relative to 10% |
Common Mistakes to Avoid
- Using the new value in the denominator instead of the original value.
- Ignoring the sign (negative means decline).
- Mixing units (e.g., comparing dollars to thousands of dollars).
- Confusing absolute change and percent change.
What If the Original Value Is Zero?
When the starting value is 0, percent change cannot be calculated with the standard formula. In reporting, people often describe this as “new from zero,” “not applicable,” or use absolute change instead. The calculator on this page handles that case and explains the result clearly.
Where Percent Change Is Used
- Finance: investment returns, revenue growth, inflation impacts.
- Business: monthly sales trends, customer growth, churn rate shifts.
- Education: test score improvements and performance tracking.
- Science: measurement changes in experiments.
- Personal life: budget changes, utility bills, and fitness progress.
Reverse Calculation (Find Original Value)
Sometimes you know the new value and the percent increase/decrease, and need the original value.
- After an increase: Original = New ÷ (1 + rate)
- After a decrease: Original = New ÷ (1 − rate)
Example: Final price is 120 after a 20% increase. Original = 120 ÷ 1.20 = 100.
Final Takeaway
The percent change calculation formula is simple but powerful:
Use it whenever you need to compare growth or decline fairly across different scales. If you want quick, accurate results, use the calculator above and double-check that your original value is the baseline in the denominator.