The original value is the baseline
Percentage change measures movement relative to where a value started. The same absolute difference can represent different percentages when the starting value changes.
Percentage change = (New − Original) ÷ |Original| × 100
Read the sign and direction
A positive result means the new value is higher, so the movement is an increase. A negative result means it is lower, so the movement is a decrease. The absolute change is simply |New − Original|.
Example: 80 → 100
- Find the change: 100 − 80 = 20.
- Divide by the original value: 20 ÷ 80 = 0.25.
- Multiply by 100: 0.25 × 100 = 25%.
The value increased by 25%.
Example: 100 → 80
- Find the change: 80 − 100 = −20.
- Divide by the original value: −20 ÷ 100 = −0.20.
- Multiply by 100: −0.20 × 100 = −20%.
The value decreased by 20%.
Increase, decrease and signed change
An increase calculator expects the new value to be larger and presents a positive growth rate. A decrease calculator expects it to be smaller and presents the size of the fall. A general change calculator keeps the sign so one formula can describe either direction.
What if the original value is zero?
The standard formula would divide by zero, so a finite percentage change is undefined. Report the absolute movement—for example, “the value rose from 0 to 10”—and explain that no conventional percentage baseline exists.
Percentage change vs. percentage difference
Use percentage change when one value is clearly the starting point. Use percentage difference when neither value is the baseline; that formula divides the absolute difference by the average of the two values.
Related calculators
Measure general change or choose a direction-specific tool.