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Percentage change calculator: increase or decrease
Calculate percentage increase or decrease between two values, with a worked example and a zero-baseline explanation.
Percentage change
Turn two numbers into a clear increase or decrease.
Change
Formula: (new − old) ÷ |old| × 100
Explainable maths
Every result uses a short, visible formula.
No hidden assumptions
Prices and usage are always yours to enter.
How to use this calculator
Enter an old value and a new value. The calculator shows the relative change and the numerical difference. A positive result means an increase and a negative result means a decrease. No currency is needed, but the two values must measure the same thing in the same units.
Worked example
A change from 120 to 150 is a difference of 30. Dividing 30 by 120 and multiplying by 100 gives a 25% increase. Going back from 150 to 120 is a 20% decrease, not 25%, because the starting value is different.
What if the starting value is zero or negative?
Percentage change from zero is undefined because the formula would divide by zero. For negative starting values, this tool divides by the absolute value of the baseline. That convention is shown explicitly and may not suit financial growth reporting.
Is percentage change the same as percentage points?
No. A rate rising from 10% to 15% increases by 5 percentage points, but by 50% relative to its starting rate. Enter 10 and 15 here to calculate the relative change, not the percentage-point difference.