Enter an old value and a new value to see the percentage increase or decrease between them, together with the actual difference between the two numbers.
Results are estimates for planning. Check the figures before you make a financial or health decision.
How the Percentage change works
Percentage change compares a new value with the old value you started from:
change % = (new − old) ÷ |old| × 100
A positive result is an increase, and a negative result is a decrease. The tool shows the size of the change as a positive percentage and labels it as an increase or a decrease. It also shows the plain difference between the two numbers.
Going from 64 to 80 is a rise of 16, and 16 ÷ 64 × 100 gives 25%.
Two points to watch:
- The old value must not be zero, because the change cannot be measured against zero.
- Percentage changes are not reversible. A 50% rise followed by a 50% fall does not take you back to where you started, because the second change applies to a larger number.
The tool works for any figures, such as prices, populations or exam scores.
Worked example
Using the default values in the calculator above:
| Input | Value |
|---|---|
| Old value | 64 |
| New value | 80 |
Increase: 25%
| Difference | 16 |
|---|---|
| Old value | 64 |
| New value | 80 |
Tips and common mistakes
Always put the starting value in the old box. Swapping them gives a different answer, and a rise of 25% does not match a fall of 25% in the other direction. Do not confuse percentage change with percentage points: moving from 4% to 5% is a rise of one percentage point but a 25% increase. For reporting, round to a sensible number of places and state the starting figure as well.
Frequently asked questions
How do I calculate percentage increase?
Subtract the old value from the new value, divide by the old value and multiply by 100. A positive answer is an increase.
Why is a 50% rise then a 50% fall not back where I started?
The fall is taken from the larger, new value. So it removes more than the rise added, and you end up lower than the original.
What is the difference between percentage change and percentage points?
Percentage points are the simple difference between two percentages. Percentage change compares them as a proportion of the old figure.