What is percentage increase?
Percentage increase tells you how much a value has grown relative to its original value. For example, if a price rises from $80 to $100, the increase is $20, which is 25% of the original $80.
Percentage increase formula
Use this formula when the new value is higher than the original value:
Percentage increase = ((New value − Original value) ÷ Original value) × 100
Example: a value increases from 80 to 100.
- Find the difference: 100 − 80 = 20.
- Divide by the original value: 20 ÷ 80 = 0.25.
- Multiply by 100: 0.25 × 100 = 25%.
What is percentage decrease?
Percentage decrease tells you how much a value has fallen relative to its original value. The original value is still the reference point.
Percentage decrease formula
Use this formula when the new value is lower than the original value:
Percentage decrease = ((Original value − New value) ÷ Original value) × 100
Example: a price falls from $120 to $90.
- Find the decrease: 120 − 90 = 30.
- Divide by the original value: 30 ÷ 120 = 0.25.
- Multiply by 100: 0.25 × 100 = 25%.
Why the original value matters
Percentage increase and decrease are measured relative to the original value. Using the new value as the denominator can produce a different percentage and answer the wrong question.
Percentage change vs. percentage of a number
These calculations are different. To find 20% of 150, calculate (20 ÷ 100) × 150. To find the percentage change from 150 to another value, compare the difference with the original 150.
For the broader set of percentage formulas, see How to Calculate Percentage: Formula & Examples.
Common examples
- A salary rises from $2,000 to $2,200: the increase is 10%.
- A product falls from $50 to $40: the decrease is 20%.
- A test score rises from 60 to 75: the increase is 25%.
- A quantity falls from 500 to 450: the decrease is 10%.
Common mistakes
- Using the new value instead of the original value as the denominator.
- Forgetting to multiply the decimal result by 100.
- Confusing percentage change with percentage points.
- Rounding too early in a calculation.
Frequently asked questions
How do I calculate percentage increase?
Subtract the original value from the new value, divide by the original value, then multiply by 100.
How do I calculate percentage decrease?
Subtract the new value from the original value, divide by the original value, then multiply by 100.
What is the formula for percentage change?
Percentage change is ((New − Original) ÷ Original) × 100. The sign indicates the direction of change.
Is a 20% increase followed by a 20% decrease back to the original value?
No. A 20% increase and a 20% decrease are calculated from different reference values, so they do not cancel each other out.
For finding X% of a number, use the free ToolAlto Percentage Calculator.
Open Percentage Calculator →