Solo Biz Soft Editorial Team Percentage change tells you how much something has grown or shrunk compared with where it started. You use it for prices, salaries, sales, weight and almost anything that changes over time. Here is the method.
The formula
Percentage change = (new value − old value) ÷ old value × 100.
Step by step
- Subtract the old value from the new value.
- Divide the result by the old value.
- Multiply by 100 to get a percentage.
- If the answer is positive it is an increase; if negative, a decrease.
Worked example
A price rises from 80 to 100. The change is 100 − 80 = 20. Divided by 80 gives 0.25, so the price rose by 25%. If it then falls from 100 back to 80, the change is −20 ÷ 100 = −20%, not −25%, because the starting value is different.
Common mistakes
- Dividing by the new value instead of the old value
- Adding percentages from different starting points
- Confusing percentage points with percentages. Going from 10% to 12% is a rise of 2 percentage points, but a 20% increase
Skip the maths: use our free percentage calculator.
Frequently asked questions
How do I calculate a percentage increase?
Subtract the old value from the new, divide by the old value and multiply by 100.
How do I increase a number by a percentage?
Multiply it by 1 plus the percentage as a decimal. To add 15%, multiply by 1.15.
How do I decrease a number by a percentage?
Multiply by 1 minus the percentage. To take off 15%, multiply by 0.85.
More free tools: browse all our free calculators.
This article is general information only.