Percent change calculator: increase and decrease
Enter the original value and the new value. From 80 to 100 is a 25% increase; from 100 to 80 is a 20% decrease. The result also shows the change needed to get back to the original.
Inputs used by this calculator
Percentage Change Calculator uses the fields below. The starting values reproduce the page example; replace them with values from the same units and time period before using the result.
| Input | Starting example | Accepted value | How it is used |
|---|---|---|---|
| Original value | 80 | 0 or greater | Supplies the original value quantity used by the published equation or result breakdown. |
| New value | 100 | 0 or greater | Supplies the new value quantity used by the published equation or result breakdown. |
The percent change formula
Subtract the original value from the new value, divide by the original value and multiply by 100. A positive result is an increase and a negative one is a decrease.
percent change = (new − original) ÷ original × 100Increases and decreases are not symmetric
A fall of 20% followed by a rise of 20% does not return to the start: 100 falls to 80, and 20% of 80 is only 16, giving 96. To recover from a 20% drop, the value must rise 25%. The table shows the rebound needed for common changes.
Percent change versus percentage points
When an interest rate moves from 4% to 5%, it rose by one percentage point but by 25 percent. Use percentage points for the difference between two percentages and percent change for the change relative to the start.
The multiplier
Dividing the new value by the original gives a multiplier: 1.25 means 25% more, 0.8 means 20% less. Multipliers make repeated changes easy to combine: two 10% increases multiply to 1.1 × 1.1 = 1.21, a 21% total increase.
When the original is zero
Percent change from zero is undefined, because nothing can be divided by zero. Report the absolute change instead, such as “from 0 to 50 sign-ups”.
Percent change versus percent difference
Percent change has a direction: from one value to another. When two values are compared without a starting point, such as two measurements of the same thing, the Percent Difference Calculator divides by their average instead.
Rebound needed to return to the original
| First change | Change needed to return |
|---|---|
| -10% | +11.11% |
| -20% | +25% |
| -25% | +33.33% |
| -50% | +100% |
| +25% | -20% |
| +50% | -33.33% |
| +100% | -50% |
Frequently asked questions
How do I calculate percent increase?
(new − original) ÷ original × 100. From 80 to 100: 20 ÷ 80 × 100 = 25%.
How do I calculate percent decrease?
Use the same formula; the result is negative. From 100 to 80 is −20%.
Why doesn't a 20% drop and a 20% gain cancel out?
The gain applies to the smaller number, so you need 25% to recover.
What is the difference between percent and percentage points?
Points measure the gap between two percentages; percent change is relative to the start.
Can percent change be more than 100%?
Yes. Doubling is a 100% increase and tripling is 200%.
What if the original value is zero?
The percent change is undefined; use the absolute change.
How do I combine two percent changes?
Multiply their multipliers: +10% and +10% give 1.21, a 21% increase.
What to keep in mind
The original value must be positive. A change from zero has no defined percentage.
Results are rounded for display in US format, with money in dollars and cents; CSV exports keep full calculation precision. This is a calculation summary, not an official certificate.