Work out any percentage in one place: a percent of a number, what percent one number is of another, and percentage increase or decrease.
To find a percent of a number, divide the percent by 100 and multiply by the number. For example, 20 percent of 200 is 0.20 times 200, which is 40. Use the calculator below to switch between the three common percentage questions and see the steps.
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How to Calculate a Percentage
A percentage is a way of writing a number as a part of 100. The word percent means "per hundred", so 20 percent is the same as 20 out of 100, or the fraction 20/100, or the decimal 0.20.
Almost every percentage question is one of three types. This calculator handles all three. Pick the mode that matches your question, enter two numbers, and it shows the answer plus the steps so you can follow the method.
The Three Percentage Formulas
Percent of a number
(P / 100) x NWhat is 20% of 200? (20 / 100) x 200 = 40.
X is what percent of Y
(X / Y) x 10050 is what percent of 200? (50 / 200) x 100 = 25%.
Increase or decrease
((B - A) / A) x 100From 200 to 250 is ((250 - 200) / 200) x 100 = 25% increase.
Worked Example
Say a 200 dollar jacket is 30 percent off. The discount is 30 percent of 200, which is (30 / 100) x 200 = 60 dollars. The sale price is 200 minus 60, which is 140 dollars. If the price later rises from 140 back to 200, that is a ((200 - 140) / 140) x 100 = 42.9 percent increase.
Common Percentages Reference
Handy values you can use to check the calculator or estimate in your head.
| Percent | As a decimal | As a fraction | Quick method |
|---|---|---|---|
| 1% | 0.01 | 1/100 | Divide by 100 |
| 5% | 0.05 | 1/20 | Half of 10% |
| 10% | 0.10 | 1/10 | Move the decimal one place |
| 20% | 0.20 | 1/5 | Double 10% |
| 25% | 0.25 | 1/4 | Divide by 4 |
| 50% | 0.50 | 1/2 | Halve the number |
| 75% | 0.75 | 3/4 | Three quarters |
Common Percentage Mistakes
- Confusing "percent of" with "percent off". A 30 percent discount means you pay 70 percent of the price.
- Reversing a percentage change. Going up 50 percent then down 50 percent does not return you to the start.
- Using the wrong base. Percentage change is always measured against the original value, not the new one.
- Forgetting to convert. To use a percent in a formula, divide it by 100 first.
- Adding percentages that have different bases, such as two discounts on different prices.
Frequently Asked Questions
How do I find a percentage of a number?
Divide the percent by 100, then multiply by the number. For 20 percent of 200, calculate 0.20 times 200, which is 40.
How do I work out what percent one number is of another?
Divide the first number by the second, then multiply by 100. For 50 out of 200, that is (50 / 200) x 100 = 25 percent.
How do I calculate percentage increase or decrease?
Subtract the old value from the new value, divide by the old value, then multiply by 100. A positive answer is an increase and a negative answer is a decrease.
What is the difference between percent off and percent of?
Percent of gives you a part of the number. Percent off subtracts that part. A 30 percent discount means you pay 70 percent of the original price.
Why do equal percentage changes not cancel out?
Because each change uses a different base. A 50 percent rise from 100 gives 150, and a 50 percent fall from 150 gives 75, not 100.
How do I turn a percentage into a decimal or fraction?
Divide the percent by 100 for the decimal, and place it over 100 then simplify for the fraction. So 25 percent is 0.25 and 1/4.
Disclaimer
This calculator is intended for general educational and practical use. Review important results before relying on them in professional, financial, or academic work.
Creator
Hamza Shakeel is the Chief Technology Officer at MultiCalculators.com, responsible for the platform's technical architecture, calculator engine performance, and infrastructure reliability. He leads engineering efforts focused on site speed, mobile responsiveness, Core Web Vitals optimization, and security. Hamza ensures every calculation runs accurately and instantly across all devices, while maintaining the platform's stability and scalability as it grows. His work directly supports the seamless, trustworthy experience users expect from MultiCalculators.com.
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