X is what percent of Y?
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Increase or decrease by a percentage
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Percentage formulas
A percentage is a number expressed as a fraction of 100. These four formulas cover almost every everyday percentage question:
Everyday uses
- Discounts: 25% off a $60 item saves $15, so you pay $45.
- Tips: a 20% tip on a $45 bill is $9.
- Pay rises: a raise from $3,000 to $3,150 a month is a 5% increase.
- Grades: 42 correct answers out of 50 is 84%.
- Sales tax and VAT: adding 8% tax to $50 gives $54.
Frequently asked questions
How do I calculate a percentage of a number?
Multiply the number by the percentage and divide by 100. For example, 15% of 80 is 80 × 15 ÷ 100 = 12.
How do I calculate percentage change?
Subtract the old value from the new value, divide by the old value, and multiply by 100. Going from 50 to 65 is (65 − 50) ÷ 50 × 100 = a 30% increase.
What's the difference between percentage change and percentage points?
Percentage points measure the plain difference between two percentages, while percentage change is relative. An interest rate going from 4% to 5% rises by 1 percentage point, which is a 25% increase.
Why doesn't a 50% drop followed by a 50% rise get me back to where I started?
Because each percentage applies to a different base. 100 minus 50% is 50, and 50 plus 50% is only 75. To get back to 100 from 50 you need a 100% increase.