PERCENTAGE CHANGE GUIDE

How to calculate percentage increase and decrease

Use the original value as the reference point, then compare the new value to it. This method works for price changes, marks, quantities, and measurements.

FORMULA

percentage change = (new value − original value) ÷ original value × 100

WORKED EXAMPLE

A price rises from 80 to 100. The change is 20. Divide 20 by 80, then multiply by 100: the increase is 25%.

STEP BY STEP

Start with the original value

The original value is the baseline. Do not divide by the new value when you are measuring percentage change.

Find the difference

Subtract original value from new value. A positive result is an increase; a negative result is a decrease.

Divide and multiply by 100

Divide the difference by the original value, then multiply by 100 to convert the result into a percentage.