Percent change between two numbers
Increase or decrease a number by a percent
About this tool
This calculator finds the percent change between a starting value and a new value, and tells you whether it is an increase or a decrease. The formula is (new value minus starting value) divided by the starting value, times 100. A second box works the other way: give it a number and a percent, and it shows the number after an increase and after a decrease. It runs in your browser and nothing is sent anywhere.
How to use it
For percent change, enter the old number on the left and the new number on the right. A positive result is an increase and a negative result is a decrease. For a markup or discount, use the second box: enter the price and the percent, then read the two results. For a plain "what is X percent of Y" question, use the percentage calculator.
The percent change formula, step by step
Take the difference between the new and old value, divide it by the old value, and multiply by 100. Going from 80 to 100 is a change of 20, divided by 80 is 0.25, which is a 25% increase. Going from 100 back to 80 is a change of -20, divided by 100, which is a 20% decrease. The two answers differ because the starting value is different each time.
Percent change examples
| Change | Percent change |
|---|---|
| 50 to 75 | +50% |
| 80 to 60 | -25% |
| 100 to 150 | +50% |
| 200 to 150 | -25% |
| 5 to 10 | +100% |
| 10 to 5 | -50% |
| 40 to 41 | +2.5% |
| 1,000 to 1,100 | +10% |
Where people need percent change
- Prices and sales: how much a price went up, or how big a discount really is.
- Business numbers: month-over-month growth in traffic, revenue or signups.
- Investments and savings: how much a balance or a stock price moved over a period.
- Grades and fitness: improvement between two test scores or two measurements.
Things to watch out for
Percent change is not symmetric. A 50% increase followed by a 50% decrease does not return you to the start: 100 becomes 150, then 75. Percent change is also undefined when the starting value is zero, because you cannot divide by zero. And do not confuse percent change with percentage points: going from 5% to 10% is a 100% increase but only 5 percentage points, as explained in this short guide.
Frequently asked questions
Subtract the old value from the new value, divide by the old value, and multiply by 100. A positive result is an increase and a negative result is a decrease.
Because the second percent applies to the new, larger number. 100 up 50% is 150, and 150 down 50% is 75, which is 25% below where you started.
Percent change cannot be calculated from zero, because dividing by zero is undefined. In that case, report the absolute change instead.