Percentage Calculator
Work out what percent one number is of another, and percentage increase or decrease.
How to use
Enter your values and pick a mode if the tool offers one.
Click calculate — results appear instantly, computed in your browser.
Copy the result or save the tool to your favorites.
Frequently asked questions
Divide X by Y and multiply by 100. For example, 25 of 200 is 12.5%.
(New − Old) / Old × 100. A move from 25 to 200 is a 700% increase.
Yes. If the second value is smaller, the percentage change is negative.
Results show two decimal places for readability.
Entirely in your browser.
About the Percentage Calculator
The Percentage Calculator is a free, browser-based tool that handles the four percentage problems people run into most often. Instead of remembering separate formulas, you pick a mode, type two numbers, and read the answer instantly. Nothing is uploaded to a server, so the calculation is private and immediate.
What each mode does
- Percent of a number: finds a percentage of a value. For example, 15% of 200 is 30. This is the everyday case for discounts, tips, commissions, and tax-inclusive pricing.
- X is what percent of Y: tells you the proportion one number represents of another. If you scored 25 out of 200, that is 12.5%. Useful for grades, test scores, market share, and progress tracking.
- Percentage increase or decrease: measures change between two values. Going from 100 to 150 is a 50% increase; the tool also reports the raw difference. This is how you express growth, price changes, and trends.
- Add or subtract a percentage: adjusts a base value up or down by a percent in one step, showing both the increased and decreased result side by side.
How percentages work
A percentage is simply a fraction out of one hundred. To find a percent of a number, convert the percent to a decimal by dividing by 100, then multiply. So 15% becomes 0.15, and 0.15 multiplied by 200 gives 30. To find what percentage one number is of another, divide the part by the whole and multiply by 100. To measure change, subtract the old value from the new value, divide by the old value, and multiply by 100.
Common uses
Percentages appear everywhere in daily life and business. Shoppers use them to work out sale prices and how much they save. Students convert marks into percentages to understand grades. Investors and analysts express returns, growth, and declines as percentage change. Business owners calculate margins, markups, GST, and commissions. Because the math is identical across all these cases, one flexible calculator covers them all.
Tips for accurate results
Make sure you are in the right mode for the question you are asking, since "15% of 200" and "15 is what percent of 200" give very different answers. When measuring change, the order matters: the starting value is always the denominator. For chained calculations such as applying two discounts, calculate the first result, then feed it back in rather than adding the percentages together, because percentages of different bases do not add directly.
For related calculations you may also find the Discount Calculator, GST Calculator, and Profit Margin Calculator useful. All of them run entirely in your browser and are completely free to use.