How to Calculate Percentage Increase and Decrease
Percentage change tells you how much something moved relative to where it started. Learn the formula and how to read the result correctly.
What is the Percentage Change Calculator?
This tool subtracts the old value from the new value, divides by the old value, and multiplies by 100. A positive result is an increase and a negative result is a decrease. The starting value must not be zero, because change from zero cannot be expressed as a percentage.
How to use it
- Enter the old (starting) value.
- Enter the new value.
- Read the percentage change and whether it is an increase or a decrease.
Worked example
Old value 80, new value 100: change 20, percentage change 25% (increase).
A price rose from 80 to 100. What is the percentage increase?
The increase is 25%. Subtract 80 from 100 to get 20, divide 20 by 80 to get 0.25, and multiply by 100. Because the new value is higher, the result is described as a 25% increase.
Frequently asked questions
What if the old value is zero?
A percentage change from zero is undefined, so the tool asks for a starting value greater than zero.
What does a negative result mean?
A negative result means the value went down, so it is a percentage decrease.