The three percentage problems
Almost every percentage question is one of three types, and this page solves all of them.
- What is X% of Y? Multiply Y by X and divide by 100. For example, 15% of 200 is 30.
- X is what percent of Y? Divide X by Y and multiply by 100. For example, 30 is 15% of 200.
- Percentage change. Subtract the old value from the new one, divide by the old value, then multiply by 100.
Where percentages are used
Discounts, tax, tips, interest rates, exam scores and statistics all rely on percentages. Getting the direction of a change right, increase versus decrease, is the most common mistake.
Frequently asked questions
How do I calculate a discount?
Use the first calculator: enter the discount percent as X and the original price as Y to get the amount off.
How do I work out percentage increase?
Use the change calculator with the original value as 'from' and the new value as 'to'.
Why is my percentage negative?
A negative result means the value decreased rather than increased.