How to calculate percent change
Compare two numbers as a percent of the starting value, and do not divide by the ending value.
Short answer
Percent change = (ending − starting) ÷ starting × 100. A rise from 80 to 100 is 25%, because the change of 20 is a quarter of 80.
Always divide by the start
Subtract first so you keep the direction. A drop from 100 to 80 is −20, and −20 ÷ 100 is −20%. A rise from 80 to 100 is +25%. The two statements describe one trip in opposite directions, and both are right because the starting points differ.
If the start is zero, stop. There is no percentage change from nothing. Report the new number itself instead of inventing a huge percent. Use the percentage calculator in change mode when you want the sign checked for you.
Common mistakes
- Dividing by the average, or by the ending value, when the question asked for change from the start.
Frequently asked questions
- Can a percent change be more than 100?
- Yes. Doubling is a 100% increase. Going from 20 to 80 is a 300% increase.