Percentage Change Calculator
Use a non-zero starting value so the percentage change is defined.
Revenue went from 84,000 to 97,500 - how much is that in percent? Stock dropped from 142 to 119 - what is the decline? Percentage change compares a new value to an old value as a fraction of the old. Sign matters: positive numbers are growth, negative numbers are a drop. This calculator takes the two values, shows the formula it used, and gives you both the percent change and the absolute delta.
How to calculate percentage change
-
1
Enter the old value
The baseline you are comparing against (last year, starting price, initial count).
-
2
Enter the new value
The current or ending number you want to measure.
-
3
Read the result
Percent change and raw delta appear immediately, with the formula shown.
-
4
Interpret the sign
Positive = increase, negative = decrease. Zero means no change.
The formula
percent_change = (new - old) / |old| * 100
The absolute value on the denominator matters when the old value is negative (debt going from -500 to -300 is a 40% improvement, not a -40% drop). If the old value is zero, percentage change is undefined - you cannot describe “going from zero to something” as a percentage of nothing.
Percentage change vs percentage difference
These are not the same thing:
| Concept | Formula | Use when |
|---|---|---|
| Percentage change | (new - old) / old * 100 |
One value is a baseline; direction matters |
| Percentage difference | ` | a - b |
Gotchas people actually hit
- Reversing growth. A 50% rise does not undo with a 50% cut. 100 -> 150 -> 75. To fully reverse, you need the inverse factor: divide instead of subtracting the same percent.
- Percent vs percentage points. Unemployment moving from 5% to 7% is a 40% change, but also 2 percentage points. Both are valid; say which you mean.
- Small base inflates percentages. Going from 2 to 3 is a 50% jump. Going from 200 to 201 is 0.5%. Same absolute change, very different framing.
- Compounding vs simple. If you chain monthly growth rates, you need to multiply
(1 + r)factors, not add the percents.
Typical use cases
- Year-over-year revenue or user growth.
- Stock or crypto price moves over a period.
- Cost savings after a process change.
- Weight change, training performance, any before/after metric.
Frequently Asked Questions
Percentage change is undefined when the baseline is zero. Report the absolute number instead, or use a log scale / growth factor if the context demands.
Yes. The calculator divides by the absolute value of the old number, so going from -200 to -150 shows as a +25% change (an improvement). Check the sign convention matches your use case.
For a single period, yes. For multi-period compounding, use CAGR (compound annual growth rate) instead - a straight percent change between two points ignores what happened in between.
Nothing leaves your browser. The math runs locally and no inputs are logged.
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