How to Calculate Percentage Change: A Complete Guide
Whether you are tracking stock performance, measuring business growth, or analyzing scientific data, calculating percentage change is essential. Here is exactly how to do it.
The Percentage Change Formula
Percentage Change = ((New Value - Old Value) / |Old Value|) x 100
A positive result means increase. A negative result means decrease.
Example: Stock Price Increase
If a stock goes from $50 to $65:
((65 - 50) / 50) x 100 = (15 / 50) x 100 = 0.3 x 100 = +30%
The stock price increased by 30%.
Example: Price Decrease
If a product drops from $200 to $150:
((150 - 200) / 200) x 100 = (-50 / 200) x 100 = -0.25 x 100 = -25%
The price decreased by 25%.
Why Use Absolute Value for the Old Value?
Using the absolute value of the old value ensures the calculation works even when the old value is negative. For example, going from -10 to +5: ((5 - (-10)) / |-10|) x 100 = (15/10) x 100 = +150%.
Common Percentage Change Scenarios
| Scenario | From to To | Change |
|---|---|---|
| Revenue growth | $100K to $150K | +50% |
| Population change | 1M to 1.2M | +20% |
| Weight loss | 200 lbs to 180 lbs | -10% |
| Test score improvement | 72% to 85% | +18.1% |
Key Takeaways
- The percentage change formula works for any two values
- A positive result means increase; negative means decrease
- Always use the absolute value of the original value as the denominator
- Use our Percentage Change Calculator for instant results