Percentage change, explained without the confusion
A simple worked example for everyday maths and revision.
Percentage change is the change divided by the original value, multiplied by 100. Always identify the starting value first.
Try a worked example
If a value rises from 80 to 100, the increase is 20. Divide 20 by the original 80 and multiply by 100: the increase is 25%.
Why reversing it is different
If 100 falls to 80, the decrease is still 20, but the starting value is now 100. So the decrease is 20%. Equal absolute changes can have different percentage changes.
A quick self-check
A price rises from 200 to 250. What is the percentage increase? The increase is 50, and 50 divided by 200 is 0.25. Multiply by 100 for 25%. If the original value is zero, this formula cannot be used.
Frequently asked questions
What is the key idea?
Percentage change is the change divided by the original value, multiplied by 100. Always identify the starting value first.