What is a percentage calculator?
A percentage calculator answers the everyday questions that are awkward to do in your head: what is 15% of a bill, what discount has been applied to a product, or how much did a value rise from last month? A percentage is simply a part of one hundred. For example, 25% means 25 out of every 100, which is the same as 0.25.
This tool puts the most common percentage calculations in one place. It works instantly as you enter numbers and runs entirely in your browser, so no values are uploaded or stored.
How to use the percentage calculator
- Choose “Percentage of a number” to find a portion, such as 20% of 80.
- Choose “One number as a percentage of another” to compare two values, such as 30 out of 120.
- Choose “Percentage change” to measure an increase or decrease between an original value and a new value.
- Enter decimal values when needed; negative values work too when they make sense for your calculation.
The answer is shown immediately with the formula underneath it, making it easier to check the result or understand the method before using it elsewhere.
How percentage formulas work
To find a percentage of a number, divide the percentage by 100 and multiply it by the number. For instance, 15% of 200 is (15 ÷ 100) × 200, or 30. To discover what percentage one number is of another, divide the first number by the second and multiply by 100. So 18 out of 60 is 30%.
Percentage change starts with the difference between the new and original values. Divide that difference by the original value, then multiply by 100. Moving from 50 to 65 is a 30% increase because the difference is 15 and 15 ÷ 50 is 0.3. Because the original value is the denominator, percentage change cannot be calculated when the original value is zero.
Why use an online percent calculator?
Percentages appear in shopping discounts, tax and tips, school grades, survey results, finance reports and performance comparisons. A calculator saves time and avoids small arithmetic mistakes, especially when a number includes decimals. It is also useful for checking a quoted sale price: calculate the discount amount, then subtract it from the original price.
All calculations on this page happen locally on your device. You can use it for personal budgets, work figures or quick estimates without creating an account or sending data to a server.