DigiKitPercentage Change Calculator
Enter the old and new value to see the percentage by which it increased or decreased.
The percentage change formula
To show how much a value changed relative to another, use percentage change: (new − old) ÷ |old| × 100. It is used for price rises, pay raises, sales changes, inflation and investment returns.
Worked examples
| Old | New | Difference | Change |
|---|---|---|---|
| 80 | 100 | +20 | 25% increase |
| 100 | 80 | −20 | 20% decrease |
| 250 | 300 | +50 | 20% increase |
| 1,500 | 1,200 | −300 | 20% decrease |
| 40 | 10 | −30 | 75% decrease |
Note the first two rows: 80 to 100 is a 25% increase, but going back from 100 to 80 is a 20% decrease. The percentage is always taken relative to the starting value, so the reverse direction gives a different rate.
Common mistakes
- Confusing percent with percentage points: 10% to 12% is 2 points, a 20% relative increase.
- Adding successive percentages: a 10% rise followed by a 10% fall ends 1% lower (110 → 99).
- Choosing the wrong base: swapping the old and new values gives a different result.
How to use it
- Enter the old (starting) value.
- Enter the new (final) value.
- Press Run to see the percentage change, the difference and the direction.
Where it helps
- Comparing prices and checking discounts
- The real size of a pay raise
- Changes in website traffic, sales and conversion
- Personal tracking such as grades or weight
For percentage and discount calculations, see the other percentage tools on the site.
Change over several years: rates do not add up
If a value rises by 10 percent two years in a row, the total rise is 21 percent, not 20: 100 becomes 110, then 121. Adding or averaging yearly rates is therefore misleading.
To find the average yearly change over several years, use the compound annual growth rate: (final value ÷ initial value) to the power of (1 ÷ number of years), minus 1. For example, a value that goes from 100 to 133.1 in 3 years grew by an average of 10 percent a year.
Frequently asked questions
How is percentage change calculated?
Formula: (new value − old value) ÷ |old value| × 100. A positive result is an increase and a negative one a decrease. Going from 80 to 100 gives (100 − 80) ÷ 80 × 100 = a 25% increase.
Is percentage increase the same as percentage points?
No. If an interest rate goes from 10% to 12% that is a 2 percentage point rise but a 20% relative increase. The tool calculates relative change.
If I rise 25% and then fall 25%, do I get back to the start?
No. 100 rising 25% gives 125; falling 25% from 125 gives 93.75, because the percentage applies to a different base. A 20% fall is needed to return to the start.
What if the old value is zero?
Percentage change from zero is undefined because it would mean dividing by zero. The tool warns you in that case.