How to calculate percentage change
- Choose “Percent change” if it is not already selected.
- Type the starting value and the final value.
- See the change in %, highlighted: positive if it went up, negative if it went down.
- Open “Show the calculation step by step” to see the formula.
The formula and examples
Percentage change is (final value − starting value) ÷ starting value × 100. From 80 to 100 it is (100 − 80) ÷ 80 × 100 = +25%; from 100 to 80 it is −20%.
It is useful for comparing prices, sales, salaries or results between two periods. Careful: going up 25% and down 25% does not bring you back to the original value, because they are calculated on different bases.
Good to know
- The starting value cannot be zero: you cannot divide by zero.
- A negative result means a decrease.
- The result is rounded to make it easy to read.
Frequently asked questions
How do you calculate the percentage increase from 80 to 100?
(100 − 80) ÷ 80 × 100 = 25%.
What if the value drops from 100 to 80?
(80 − 100) ÷ 100 × 100 = −20%, a 20% decrease.
Why doesn’t going up and down by the same percentage bring me back to the start?
Because the second percentage is calculated on a different value: +25% of 80 is 100, but −25% of 100 is 75.
Is my data sent to any server?
No. The calculation runs in your browser.