Percentage change measures how much a value went up or down relative to where it started. Subtract the old value from the new one, divide by the old value and multiply by 100. A positive result is an increase and a negative one is a decrease: going from 150 to 180 is a 20% increase.
Formula
% change = (new − old) ÷ |old| × 100 Examples
- A price goes from 40 to 50: (50 − 40) ÷ 40 × 100 = +25%.
- Monthly visitors drop from 12,000 to 9,000: (9,000 − 12,000) ÷ 12,000 × 100 = −25%.
Common mistakes
- Dividing by the new value. From 40 to 50 is +25%, but from 50 to 40 is −20%.
- Adding changes together. +10% and then another +10% is +21% overall, not +20%.
- Using percent change when neither value is the starting point. Then you want the percentage difference.
In Excel and Google Sheets
- Old value in A2, new value in B2 (format as %)
=(B2-A2)/ABS(A2)
FAQ
Is percentage change the same as percentage difference?
No. Percentage change compares a new value with an old one, so the order matters. Percentage difference compares two values with no order and divides by their average.
Can a percentage change be more than 100%?
Yes, for increases: going from 50 to 150 is +200%. A decrease can’t go past −100% unless the value turns negative.
What if the starting value is 0?
Then the percentage change is undefined, because you can’t divide by 0. Describe the change in absolute numbers instead.
How we calculate: exact decimal math (no rounding errors), you choose the decimal places, and your numbers never leave your browser. Methodology →
Updated October 2026