Percentage Change Calculator
Technical Calculation Methodology and Tool
Interactive Percentage Change Calculator
Calculate percentage increase or percentage decrease between two numbers instantly.
Percentage Change Calculator
Calculate the % increase or decrease between two values
Whether you are comparing this month's sales to last month's, checking how much a product price has changed, or tracking progress toward a goal, percentage change tells the real story. This calculator gives you the answer instantly and shows whether the result is an increase or a decrease.
How to Use This Calculator
- Enter the original or starting value in the first field.
- Enter the new or ending value in the second field.
- The calculator automatically applies the percentage change formula.
- Your result appears instantly along with the formula and a breakdown.
What Is Percentage Change?
Percentage change measures how much a number has increased or decreased relative to its starting point. It is commonly used for prices, revenue, traffic, conversion rates, population changes, costs, profits, and test scores.
A positive result means the value increased. A negative result means the value decreased. This makes percentage change one of the most useful ways to compare movement between two numbers of different sizes.
The Percentage Change Formula
The vertical bars around the old value mean we use the absolute value of the starting number. This avoids sign issues when the original number is negative.
Step-by-Step Calculation
- Subtract the starting value from the ending value to find the difference.
- Divide that difference by the absolute value of the starting value.
- Multiply the result by 100.
- Interpret the sign: positive means increase, negative means decrease.
Worked Examples
A coffee that cost $3.50 last year now costs $4.20. What is the percentage increase?
Result: +20% increase.
A TV was $1,200 and is now $900. What is the percentage decrease?
Result: −25% decrease.
Your store made $8,400 last month and $10,500 this month. What is the growth rate?
Result: +25% growth.
A student's score changed from 88 to 77. What is the percentage change?
Result: −12.5% decrease.
Results Table
| Starting Value | Ending Value | Difference | % Change |
|---|---|---|---|
| 50 | 75 | 25 | +50% |
| 80 | 60 | -20 | -25% |
| 3.5 | 4.2 | 0.7 | +20% |
| 88 | 77 | -11 | -12.5% |
Common Mistakes to Avoid
- Using the wrong base: Always divide by the original value, not the new one.
- Confusing percentage change with percentage points: A move from 10% to 15% is 5 percentage points, not 5% change.
- Ignoring the sign: Positive means increase, negative means decrease.
- Trying to divide by zero: Percentage change is undefined when the original value is zero.
Quick Answers
What is the percentage change from 50 to 75? +50%
What is the percentage change from 80 to 60? -25%
What is the percentage change from 1,200 to 900? -25%
What is the percentage change from 3.5 to 4.2? +20%
Percentage Change vs Percentage Points
If a store's discount rate changes from 10% to 15%, that is a change of 5 percentage points, but the discount rate itself increased by 50%. These are very different measurements, and using the wrong one can mislead readers or customers.