Percentage Change Calculator
Measure the percentage increase or decrease between an old value and a new value.
What the Percentage Change Calculator does
Percentage change compares a new value to an original one, expressed relative to the original. It is the standard way to report growth in revenue, price moves, population and test scores.
Formula
Percentage change = ((New − Old) ÷ |Old|) × 100
Inputs explained
| Input | Unit | Required | Notes |
|---|---|---|---|
| Original value | number | Yes | — |
| New value | number | Yes | — |
How to use it
- Enter Original value and New value.
- Select Calculate.
Worked example
Monthly revenue rises from $12,500 to $14,375.
- Original value
- 12500
- New value
- 14375
(14,375 − 12,500) ÷ 12,500 × 100 = 15% increase.
Reading the result
- A percentage increase and the matching percentage decrease are not mirror images around the same base — a 50% increase from 100 reaches 150, but a 50% decrease from 150 only returns to 75, because each percentage is calculated against a different starting value.
Common mistakes
- Assuming an X% increase followed by an X% decrease returns to the original value. It does not, except when X is zero, because the decrease is calculated against the larger, already-increased number.
Frequently asked questions
What if the original value is negative?
This calculator divides by the absolute value of the original, so the sign of the change reads intuitively. Percentage change on negative bases is often better reported as an absolute change.
Is percentage change the same as percentage difference?
No. Percentage change has a clear before and after. Percentage difference compares two values with no ordering and divides by their average.