Quick Percentage Change Tool
Enter an original value and a new value to find the percentage increase or decrease.
Tip: If your original value is 0, percentage change is undefined because division by zero is not possible.
What is percentage change?
Percentage change tells you how much a value has increased or decreased relative to where it started. It is one of the fastest ways to compare change across different scales—prices, test scores, revenue, body weight, population, and more.
Instead of just saying a value went from 40 to 50 (an increase of 10), percentage change tells you this is a 25% increase. That context makes comparisons much clearer.
The formula
- If the result is positive, it is a percentage increase.
- If the result is negative, it is a percentage decrease.
- If the result is zero, there was no change.
Examples
Example 1: Increase
Original value: 200
New value: 250
Difference: 50
Percentage change: (50 / 200) × 100 = 25%
Example 2: Decrease
Original value: 120
New value: 90
Difference: -30
Percentage change: (-30 / 120) × 100 = -25%
Common real-world use cases
- Personal finance: Track savings growth or spending reductions.
- Investing: Measure stock gains/losses from purchase price.
- Business: Compare monthly revenue, costs, or conversion rates.
- Education: Evaluate score improvements between exams.
- Health: Monitor changes in metrics like weight or cholesterol.
Quick reference table
| Original | New | Absolute Change | Percentage Change |
|---|---|---|---|
| 50 | 75 | +25 | +50% |
| 300 | 240 | -60 | -20% |
| 1,000 | 1,050 | +50 | +5% |
Common mistakes to avoid
- Using the new value as the denominator (the original value should be the base).
- Confusing percentage points with percent change.
- Forgetting that an increase and a decrease of the same percent are not symmetrical (e.g., +50% then -50% does not return to the starting value).
- Trying to calculate percentage change from an original value of 0.
FAQ
Is percentage change the same as percent difference?
Not exactly. Percentage change is directional and compares against the original value. Percent difference usually compares two values without emphasizing direction and may use their average as the base.
Can percentage change be more than 100%?
Yes. If the new value is more than double the original, the increase is greater than 100%.
Why is zero not allowed as the original value?
The formula divides by the original value. Division by zero is undefined, so percentage change cannot be computed in the usual way.