Percentage Change Calculator
Calculate the percentage change from an old value to a new value and identify whether the result is an increase or decrease.
How it works
Percentage change = (new value − old value) ÷ |old value| × 100.
Formula / calculation method
percentage change = (new − old) ÷ |old| × 100
Worked examples
- Changing from 100 to 120 is a 20% increase.
- Changing from 100 to 80 is a 20% decrease.
When this tool helps
Useful for prices, metrics, revenue, traffic, measurements, performance indicators, scientific comparisons, and before-versus-after analysis.
Related calculations: percentage increase or decrease, discount calculator, and tip calculator.
Browse this topic: Percentage, Ratio & Finance Calculators · Percentage & Finance Formula Guide.
Quick reference
| Input | Result |
|---|---|
| 100 → 120 | +20% |
| 100 → 80 | −20% |
| 50 → 75 | +50% |
Accuracy and definitions
The denominator uses the magnitude of the old value. Percentage change from an old value of zero is undefined because it would require division by zero.
Methodology & verification
- Method
- Percentage change = (new value − old value) ÷ |old value| × 100.
- Verification
- The displayed formula is cross-checked against Solveberry regression cases before release. Calculator inputs and results stay in the browser.
- Last reviewed
- 2026-08-19
Results are calculated locally in your browser. Optional analytics do not include calculator input values or results.
Common questions
Why can't I calculate percentage change from zero?
The standard formula divides by the old value, so an old value of zero makes the percentage undefined.
Is percentage change the same as percentage-point change?
No. Percentage points compare two percentages directly; percentage change measures the relative change from an original value.
Can I use decimal values?
Yes. The calculator accepts decimal values where they are mathematically valid for the selected calculation.
How should I verify an important result?
Use the displayed formula to reproduce the calculation independently, especially before making financial, legal, engineering or other consequential decisions.