Percentage change tells you how much something has grown or shrunk compared with where it started. You see it in price changes, salary offers, website traffic and investment returns. The method is the same every time.
The formula
A positive answer is an increase. A negative answer is a decrease.
Example 1: a price increase
A subscription goes from $40 to $46 a month.
- Difference: 46 − 40 = 6
- Divide by the old value: 6 ÷ 40 = 0.15
- Multiply by 100: 15% increase
Example 2: a decrease
Website visits drop from 8,000 to 6,000 a month.
- Difference: 6,000 − 8,000 = −2,000
- Divide by the old value: −2,000 ÷ 8,000 = −0.25
- Multiply by 100: 25% decrease
Mistake 1: dividing by the wrong number
Always divide by the starting value. If you divide by the new value instead, you will understate increases and overstate decreases.
Mistake 2: averaging percentages
If something rises 50% one year and falls 50% the next, you are not back to even. Starting at 100, a 50% rise gives 150, and a 50% fall takes it to 75. That is a 25% loss overall. When changes stack, multiply the growth factors (1.5 × 0.5 = 0.75) rather than adding the percentages.
Mistake 3: confusing percent with percentage points
If unemployment moves from 4% to 5%, it rose by 1 percentage point, which is a 25% relative increase. Both statements are true, but they mean different things, so be clear about which one you are reporting.
Spreadsheet formula
If the old value is in cell A2 and the new value is in B2:
Format the result cell as a percentage. The ABS function keeps the sign meaningful when the starting value is negative.
When percentage change does not work
You cannot calculate a percentage change from zero, because dividing by zero is undefined. In that case, report the absolute change instead, or say the value "started from zero".
For a quick answer, use the percentage calculator.