About the Percentage Change Calculator
Percentage change tells you how much a number has grown or shrunk compared with where it started. A price going from 80 to 100 is a 25 percent rise, and a score falling from 50 to 40 is a 20 percent drop. This calculator has three modes. The first finds the percent change from an old value to a new one. The second finds the percentage difference between two values when neither is the starting point. The third works the other way, taking a number and raising or lowering it by a percentage you choose, as you would for a price rise or a discount.
Updated October 2026
How to use the Percentage Change Calculator
- 1Pick the mode: change, difference or apply a percentage.
- 2For a change, enter the old value and the new value.
- 3For a difference, enter the two values in either order.
- 4To apply a percentage, enter the starting number, the percentage and whether to increase or decrease it.
- 5Read the result and the extra lines for the absolute change.
Everyday uses
- Price rises and sales: see how much a product changed and by what share.
- Salary and rent reviews: express a raise as a percent to compare it with inflation.
- School and sport: compare this season with the last.
- Business results: growth in sales, traffic or customers month on month.
Avoiding common slips
Always divide by the starting value, not the new one. Mixing the two gives a number that looks plausible but is wrong. Keep in mind the difference between percentage points and percent: moving from 10 percent to 12 percent is a rise of 2 percentage points but a 20 percent increase.
More percentage tools
The Percentage Calculator handles what-is-X-percent-of-Y questions, the Discount Calculator shows sale prices, the CAGR Calculator turns a long-term change into a yearly rate, and the Percent Error Calculator compares a measured value with an accepted one.
Features
- Percent increase or decrease from old to new
- Symmetric percentage difference
- Add or subtract a percentage from any number
- Shows the absolute change as well
- Handles negative numbers
- Explains impossible cases such as a start of zero
Frequently asked questions
What is the formula for percentage change?
Subtract the old value from the new value, divide by the old value and multiply by 100. Going from 80 to 100 gives (100 − 80) ÷ 80 × 100, which is 25 percent. A negative answer means the value went down.
What is the difference between percentage change and percentage difference?
Percentage change has a clear starting point and measures growth from it. Percentage difference compares two numbers that have no order, dividing their gap by their average. Use change for before and after, and difference for comparing two peers.
Why is the percentage different going up and going down?
Each percentage is measured against a different base. A rise from 100 to 150 is 50 percent, but falling back from 150 to 100 is only 33.3 percent. That is why a 50 percent loss needs a 100 percent gain to break even.
Can I calculate a change from zero?
Not as a percentage, because dividing by zero is impossible. The calculator explains this instead of giving a misleading number. You can still report the absolute change, such as an increase of 5 units.
How do I increase a number by 15 percent?
Multiply it by 1.15. So 200 increased by 15 percent is 230. To reduce it by 15 percent, multiply by 0.85 and get 170. The apply mode does the sum and shows how much was added or removed.
How are negative starting values handled?
The calculator divides by the absolute value of the old number, so a move from −50 to −25 shows as an increase of 50 percent. Percent change gets hard to interpret when values cross zero, so state your reasoning if you report it.