What is X% of Y?
X is what percent of Y?
Percentage change from X to Y
Percentage formulas
A percentage is a number expressed as a fraction of 100. These are the three formulas this calculator uses:
| Question | Formula | Example |
|---|---|---|
| What is X% of Y? | X ÷ 100 × Y | 15% of 80 = 12 |
| X is what % of Y? | X ÷ Y × 100 | 12 is 15% of 80 |
| Percentage change | (New − Old) ÷ Old × 100 | 50 to 65 = +30% |
Percentage increase and decrease
To find a percentage increase, subtract the old value from the new value, divide by the old value and multiply by 100. A price that rises from $80 to $100 is a 25% increase.
A decrease works the same way with a negative result: from $100 to $80 is a 20% decrease. The two are not mirror images, because the percentage is always measured against the starting value.
Use the third box above for both. Looking for a pay rise? Try the salary raise calculator.
📖 Guide: How to Calculate Percentage Increase and Decrease
Last updated
Frequently asked questions
How do I calculate a percentage of a number?
Divide the percentage by 100 and multiply by the number. For example, 15% of 80 is 0.15 × 80 = 12.
How do I calculate a percentage increase or decrease?
Subtract the old value from the new value, divide by the old value, then multiply by 100. A positive result is an increase and a negative result is a decrease.
What is the difference between percent and percentage points?
Going from 10% to 12% is a 2 percentage point rise, which is a 20% relative increase (2 ÷ 10 × 100).
What percentage is X of Y?
Divide X by Y and multiply by 100. For example, 12 out of 80 is 12 ÷ 80 × 100 = 15%.
Why doesn't a 50% increase followed by a 50% decrease return to the start?
Because the second percentage is taken from a larger number. 100 up 50% is 150, and 150 down 50% is 75.
Related calculators
Discount Calculator · Salary Raise Calculator · Tip Calculator
More in Money & Work.