Percentage Calculator
Find a percentage of a number, or the change between two values.
Result
30
- 150 plus 20%
- 180
- 150 minus 20%
- 120
20% of 150 = 30
How to use the Percentage Calculator
- Choose the question you want to answer from the list.
- Enter your two values in the boxes. Both have example numbers to start from.
- Read the result, which updates as you type.
- Press the copy button to keep the answer with a short sentence describing it.
About the Percentage Calculator
Percentages show up everywhere: discounts, exam marks, tips, interest rates and price changes. This percentage calculator answers the three questions people ask most often. What is X percent of Y? X is what percent of Y? And by what percentage did a value go up or down? Pick a question, enter two numbers, and see the answer straight away.
Each question uses one simple formula. To find X percent of Y, multiply: X × Y ÷ 100. So 20% of 150 is 20 × 150 ÷ 100 = 30. To find what percent X is of Y, divide and multiply by 100: X ÷ Y × 100. So 15 is 25% of 60.
Percentage change compares an old value with a new one: (new − old) ÷ |old| × 100. Going from 80 to 100 is a 25% increase, but going from 100 back to 80 is only a 20% decrease, because the starting point is different. If the starting value is zero the change cannot be expressed as a percentage, so the tool asks for a different value. Results are shown with up to six decimal places.
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 200 is 15 × 200 ÷ 100 = 30.
Why is a 25% increase not undone by a 25% decrease?
The second percentage is taken from the new, larger value. Raising 80 by 25% gives 100, and cutting 100 by 25% gives 75, not 80. A 20% decrease is needed to return to 80.
Can I use negative numbers?
Yes. A negative percentage gives a negative amount, and a change between negative values is measured against the size of the starting number.
What does percentage points mean?
A percentage point is the plain difference between two percentages. Moving from 10% to 12% is 2 percentage points, but it is a 20% relative increase.
Why does the tool refuse to divide by zero?
A value cannot be a percentage of zero, and a change from zero has no percentage. The tool shows a message instead of an incorrect number.