Percentage change, or applying one
Works out the percentage change between an original and a new value, or applies a percentage increase or decrease to a starting value — and shows the percentage that would be needed to undo the change again, since it's rarely the same number.
How to use
- Choose whether you're comparing two values or applying a percentage change
- Enter the values or the starting value and percentage
- Check the working panel for the formula used and the reverse-change figure
Common questions
If a value rises 25% and then falls 25%, does it return to where it started?
No. Increasing 100 by 25% gives 125, but decreasing 125 by 25% only brings it back to 93.75 — the second percentage is measured against the larger, already-increased number, not the original 100. The tool's "to get back to" row shows the actual percentage that would undo the change.
What's the difference between this and the plain Percentage Calculator?
This tool is built specifically around before/after values and up/down changes, with a formula that always uses the starting value as the base. The Percentage Calculator instead covers four unrelated percentage questions, including percentage difference, which uses the average of the two numbers as its base rather than the first one.