Percentage Change Calculator
Calculate the percentage increase or decrease between two values.
How much something changed, in percent
Percentage change expresses the difference between an old and a new value as a percentage of the original, so you can see the size of a change relative to where it started. This calculates the increase or decrease between two values.
Enter the old and new values to find the percentage change.
The base matters, and the asymmetry
The key to percentage change is that it is always measured against the original value, not the new one — a rise from 100 to 150 is a 50 percent increase because the 50 is compared to the starting 100. Getting the base wrong is the commonest error. There is also a genuine asymmetry that surprises people: a percentage increase and the same percentage decrease do not cancel out. A 50 percent rise followed by a 50 percent fall does not return to the start, because the fall is calculated on the larger amount, so it removes more than the rise added. This is why a stock that drops 50 percent needs to double, a 100 percent gain, just to recover. Understanding that percentage changes are relative to their base prevents a whole family of real financial misjudgements.
Percentage Change Calculator FAQ
What is percentage change measured against?
Always the original value — a rise from 100 to 150 is a 50 percent increase because the change is compared to the starting 100, not the new figure.
Why don't a percentage rise and fall cancel out?
Because the fall is calculated on the larger amount — a 50 percent rise then a 50 percent fall lands below the start, which is why a halved stock must double to recover.
Is anything uploaded?
No. The calculation happens in your browser.