Enter a number, choose increase or decrease, and type the percentage. You get the new value, the multiplier behind it and, if you repeat the change, the result after each step.
Results are estimates for planning. Check the figures before you make a financial or health decision.
How the Percentage increase and decrease works
The calculator turns the percentage into a multiplier and multiplies your starting number by it.
- Increase by x%: multiplier = 1 + x ÷ 100. An increase of 10% is × 1.1.
- Decrease by x%: multiplier = 1 − x ÷ 100. A decrease of 10% is × 0.9.
If you set the number of times above 1, the same multiplier is applied again to each new result, so the changes compound. The overall multiplier is the single multiplier raised to that power, and the overall percentage change is that figure minus 1, times 100.
The tool also shows the percentage change that would bring you back to the starting number. That is 1 ÷ overall multiplier − 1, and it is never the same as the original percentage unless the change is zero.
Limits: the percentage must be positive (use the increase/decrease choice for direction), a decrease cannot exceed 100%, and repeats are limited to 50. To find the percentage change between two known numbers, use the separate percentage change calculator.
Worked example
Using the default values in the calculator above:
| Input | Value |
|---|---|
| Starting number | 200 |
| Change | Increase by |
| Percentage | 10 % |
| Number of times to apply it | 1 |
Result: 220
| Multiplier for one change | × 1.1 |
|---|---|
| Change in the number | +20 |
| Overall change | +10% |
| Change needed to get back to the start | −9.0909% |
Tips and common mistakes
Remember that a percentage is always taken of the number it is applied to. A 20% rise followed by a 20% fall leaves you below where you began, because the fall is taken from the larger figure. Use the “back to the start” row to see the change needed to reverse any move.
For repeated changes, such as three years of 5% growth, set the number of times rather than adding the percentages together: three rises of 5% give more than 15% overall. Check that you have chosen increase or decrease before you read the result, as that is the most common slip.
Frequently asked questions
How do I increase a number by a percentage?
Multiply it by 1 plus the percentage as a decimal. To increase by 8%, multiply by 1.08. The calculator does this and shows the multiplier.
Why does a 10% rise then a 10% fall not get me back to the start?
The fall is 10% of the new, larger number, so it takes off more than the rise added. The result is 99% of the start. The calculator’s back-to-the-start row shows the exact change needed.
Can I decrease by more than 100%?
No. Decreasing by 100% takes a number to zero, and more than that would make it negative, so the calculator asks for 100 or less.
Guides that help
- Percentage increase and decrease, and reverse percentages
- Percentage change, increases and discounts
- How to calculate percentages