Percentage Change Calculator
Find the percentage increase or decrease between two values, with the absolute difference.
Results
Percentage change
25.0000
%
Difference
20
What this tool does
Percentage change compares a new value against an old one and says how much it moved, relative to where it started. A positive answer is an increase, a negative answer is a decrease, and the old value is always the reference — which is why the same absolute difference gives a different percentage depending on the direction.
Formula
c = (b − a) ÷ a × 100
Variables
| Symbol | Meaning | Unit |
|---|---|---|
a | Old value | — |
b | New value | — |
c | Percentage change | % |
d | Difference | — |
Worked example
- Old value80
- New value100
- Percentage change25.0000 %
- Difference20
Limitations
- The calculation runs at full precision and only the display is rounded. If you copy an intermediate value and retype it, small differences can appear.
Frequently asked questions
Why is a 50 % fall not cancelled by a 50 % rise?
Because each percentage is measured against a different starting point. Falling from 100 to 50 is a 50 % drop; rising 50 % from 50 gets you back to only 75. To undo a 50 % fall you need a 100 % rise. This asymmetry is why investment losses hurt more than equivalent gains help.