How to calculate percentage increase
Percentage increase tells you how much a number has grown compared with where it started. Subtract the old value from the new value, divide by the old value, then multiply by 100.
(new − old) ÷ old × 100
Examples
- A price goes from 80 to 100. (100 − 80) ÷ 80 × 100 = 25% increase.
- A monthly salary goes from 3,000 to 3,300. (3,300 − 3,000) ÷ 3,000 × 100 = 10% increase.
- A number drops from 50 to 40. (40 − 50) ÷ 50 × 100 = −20%, a 20% decrease.
Why going back down is a different percentage
The percentage always compares with the starting number, so the same gap gives different percentages in each direction. If a price rises from 100 to 150, that is a 50% increase. Going back from 150 to 100 is a drop of 50, but measured against 150 it is only a 33.3% decrease.
Common questions
How do I calculate a percentage decrease?
Use the same formula. Subtract the old value from the new value, divide by the old value, and multiply by 100. The answer is negative when the number went down.
Why can't the starting number be zero?
The formula divides by the starting number, and dividing by zero has no answer. Growth from zero can't be described as a percentage.
Is percent change the same as percentage points?
No. Percentage points are the plain difference between two percentages. Percent change compares the new value with the old one, so a rate moving from 4% to 6% is 2 percentage points but a 50% increase.