๐ Percentage Change Calculator
Enter a "before" value and an "after" value, and this tool automatically calculates the percentage change and the difference between them. Handy for comparing year-over-year sales, tracking weight changes, or checking shifts in website traffic.
How to use
- Enter the "before" value.
- Enter the "after" value.
- The difference and percentage change are shown automatically.
How the calculation works
This tool calculates how much a value went up or down, as a percentage of where it started. Percentage change = (new โ old) รท |old| ร 100 A positive result is an increase and a negative one a decrease. Dividing by the absolute value of the old value keeps the direction correct even when the starting value is negative (such as a loss). The percentage change describes the change relative to the starting point, so the same absolute difference is a bigger percentage when the starting value is smaller.
Worked example
80 โ 100: (100 โ 80) รท 80 ร 100 = +25% 100 โ 80: (80 โ 100) รท 100 ร 100 = โ20% The same difference of 20 gives different percentages. A price that rises 20% and then falls 20% goes 100 โ 120 โ 96 โ it does not return to where it started.
Things to be aware of
- Differences between rates are expressed in percentage points: an interest rate going from 2% to 3% is a 1 percentage point rise, but a 50% increase.
- An old value of 0 cannot be used, since that would mean dividing by zero.
- For an average yearly growth rate over several years, use a compound annual growth rate (CAGR) calculation.
FAQ
How is the percentage change calculated?
Using the formula (after โ before) รท |before| ร 100.
How is a decrease shown?
It's shown as a negative value with a "Decrease" label.
What happens if the before value is 0?
That would require dividing by zero, so no result is shown.