How to calculate percentage change
Percentage change works in both directions: change % = (new − old) ÷ |old| × 100. A positive answer is an increase, a negative one a decrease. Going from 120 to 90 is (90 − 120) ÷ 120 × 100 = −25%, a 25% drop.
The denominator is always the original value, because the change is measured relative to where you started. Dividing by the new value is the commonest error and would give about −33% here. To take a plain share of a number rather than compare two of them, use the percentage calculator.
How to use this calculator
Enter the original and new values. The result shows the percent change with its sign and the absolute difference, so you can tell at a glance whether it rose or fell and by how much.
The absolute value in the denominator means negative starting figures still behave sensibly: a move from −50 to −25 registers as +50%. The two values must share a unit.
Change is not symmetric
A drop and a recovery of the same percentage don't cancel out. Falling 25% from 120 to 90, then rising 25% from 90, only reaches 112.5 — not 120. For increases specifically, see the percentage increase calculator; year on year, the YoY growth calculator.
To undo a 25% fall you need a 33.3% rise, because the recovery is measured against the smaller base. The asymmetry grows with size: a 50% loss needs a 100% gain to break even.
Frequently asked questions
- How do I calculate percentage change?
- Subtract the old value from the new, divide by the absolute value of the old, then multiply by 100. From 120 to 90 is −25%.
- What does a negative percentage change mean?
- It means the value decreased. A −25% change is a 25% drop from the original.
- Why don't equal percentage rises and falls cancel out?
- Because each percentage is taken from a different base. A 25% fall then a 25% rise lands below the start, since the rise applies to the smaller number.
- What is the difference between percentage change and percentage increase?
- Percentage increase assumes growth; percentage change handles both increases and decreases with a signed result.
- What happens if the original value is zero?
- Percentage change is undefined, because dividing by zero has no meaning — any rise from nothing is infinite in percentage terms. Report the absolute change instead, or use percentage points if both figures are already percentages.