Percentage Change Calculator

Calculate the percentage increase or decrease between two numbers instantly.

Initial Value (Old)
New Value
Percentage Change
25%
25 Absolute Difference
-100%
No Change
+100%
Increase (Growth)

How to Calculate Percentage Change

Percentage change is a simple mathematical concept used to describe the degree of change over time. It is used frequently in finance to track stock prices or in retail to show discounts.

  • The Formula: Percentage Change = ((New Value - Old Value) / |Old Value|) × 100
  • Increase vs. Decrease: If the result is a positive number, it's an increase. If the result is negative, it's a decrease.
  • The "Old Value" Rule: You must always divide by the original value, not the new one. Dividing by the new one gives you a different statistic called "Percentage Error."
  • Zero Reference: If the original value is 0, the percentage change is mathematically undefined (infinity), as you cannot divide by zero.