Percentage Change Calculator
Enter your starting value and ending value to calculate the percentage increase or decrease.
What is percentage change?
Percentage change tells you how much a value increased or decreased relative to where it started. It is one of the most useful calculations in finance, business, school, and daily life because it gives context, not just raw difference.
For example, if a price goes from 50 to 75, the change is 25. But saying it changed by 50% is more meaningful, because it tells you that the increase was half the original value.
The formula for percentage change
If the final percentage is positive, it is an increase. If it is negative, it is a decrease.
Step-by-step method
- Subtract the original value from the new value.
- Divide that result by the original value.
- Multiply by 100 to convert to a percentage.
Worked examples
Example 1: Percentage increase
Original = 80, New = 100
(100 − 80) = 20
20 / 80 = 0.25
0.25 × 100 = 25%
Result: a 25% increase.
Example 2: Percentage decrease
Original = 200, New = 150
(150 − 200) = -50
-50 / 200 = -0.25
-0.25 × 100 = -25%
Result: a 25% decrease.
Common mistakes to avoid
- Using the new value as the denominator: always divide by the original value for standard percentage change.
- Forgetting the ×100 step: decimal results like 0.15 mean 15%.
- Confusing percentage change with percentage points: going from 10% to 15% is a 5 percentage-point increase, but a 50% percentage increase.
- Ignoring sign: negative means decrease, positive means increase.
Special case: original value is zero
If your original value is 0, percentage change is not defined with the standard formula because you cannot divide by zero. In that case, describe the change using absolute numbers, or use a different metric that fits your context.
Where percentage change is used
- Stock and crypto returns
- Monthly budget tracking
- Sales growth reports
- Website traffic analytics
- Weight loss or fitness progress
- Test score improvement
Quick interpretation guide
- +10% means the new value is 10% higher than the original.
- -10% means the new value is 10% lower than the original.
- 0% means no change.
Final takeaway
If you remember one thing, remember this: percentage change compares the difference to the starting point. Use the calculator above whenever you want a fast answer, then use the formula to check your understanding.