About the Percentage Change Calculator
Percentage change measures how much a value has gone up or down relative to where it started. Enter the old and new numbers to see the percent increase or decrease and the absolute change.
How it’s calculated
Percentage change = (ending − starting) ÷ starting × 100.
Example calculation
Going from 80 to 100 is a 25% increase; going from 100 to 80 is a 20% decrease.
Frequently asked questions
Why isn't an increase and decrease the same percent?
Because the starting value differs. 80→100 is +25% (÷80), but 100→80 is −20% (÷100). The base you divide by changes the result.
What if the starting value is zero?
It can't be calculated from a starting value of zero — that would mean dividing by zero. Any move up from zero is often described as an infinite percent increase instead.
This tool provides estimates for general informational and educational purposes only. Results are based on the values you enter and standard formulas, and may not reflect your specific circumstances.