About the Percentage Calculator
This page collects the percentage calculations people need most often in one place: a percentage of a number, what percent one number is of another, the percentage change between an old and a new value, increasing or decreasing a value by a percentage, the symmetric percentage difference between two values, and the price after a discount.
Each calculator updates as you type and shows the formula it used, so you can follow and check the calculation. Results are rounded to 10 significant digits to hide floating-point artifacts (0.1 + 0.2 is shown as 0.3), and each one has its own copy button.
The calculations run in your browser. The results are for general information; for tax, finance or legal purposes check the rounding rules that apply to you.
How to use it
- Find the calculator that matches your question, for example "What is X% of Y?" or "Percentage change".
- Type the numbers into its fields. Use a dot for decimals; commas are accepted as thousands separators (1,234.5). A trailing % sign in percentage fields is ignored.
- Read the result and the formula below the fields. Invalid input is marked with a message next to the field.
- Click Copy next to a result to copy it, or Clear in the corner of a card to empty its fields.
Features
- Six calculators: Percent of a number, X as a percent of Y, percentage change, increase/decrease by a percentage, percentage difference and discount with the amount saved.
- Formulas shown: Every result comes with the calculation written out with your numbers, e.g. (100 − 80) ÷ |80| × 100 = 25%.
- Careful number handling: Thousands separators, negative numbers and scientific notation (1e6) are accepted; text that is not a number gets a clear message instead of a wrong result.
- Division by zero explained: If a calculation divides by zero, for example a change from 0, the tool says so instead of showing Infinity.
- Clean results: Up to 10 significant digits with trailing zeros removed, thousands separators, and scientific notation for very large or very small values.
Examples
Tip or tax
What is 18% of 64.50? The first calculator gives 11.61 (64.5 × 18 ÷ 100).
Exam score
42 points out of 56: the "X is what percent of Y?" calculator shows 75%.
Price increase
A subscription went from 8.99 to 10.99. Percentage change shows +22.24694105%, an increase of 2. A 15% increase of 200 is 230.
Sale price
A 59.99 jacket with 25% off costs 44.9925, about 44.99, and you save 14.9975, about 15.00.
Limitations and notes
- Decimal commas (as in 12,5) are not accepted, to avoid confusing them with thousands separators. Write 12.5 instead.
- Results are rounded to 10 significant digits for display. Very large or very small results are shown in scientific notation such as 1.5e+21.
- Percentage change divides by the absolute value of the starting number, so a rise from −50 to −25 is +50%. A change from 0 cannot be expressed as a percentage.
- The discount calculator does not round to a currency; shops may round each item or the total differently.
- Results are for general information and are not financial advice.
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 200 × 15 ÷ 100 = 30.
What is the difference between percentage change and percentage difference?
Percentage change compares a new value with an old one: (new − old) ÷ |old| × 100, and its sign shows an increase or decrease. Percentage difference compares two values without a direction: the absolute difference divided by their average. From 40 to 50 is a 25% change, but the percentage difference between 40 and 50 is 22.22%.
Why is a 20% increase followed by a 20% decrease not the original value?
The second percentage is taken from a larger number. 100 increased by 20% is 120, and 120 decreased by 20% is 96. To undo a 20% increase you need a decrease of about 16.67%.
How do I work out the original price before a discount?
Divide the sale price by (1 − discount ÷ 100). If an item costs 75 after 25% off, the original price was 75 ÷ 0.75 = 100. You can check it with the discount calculator.
Why can't I calculate the percentage change from 0?
The change is divided by the starting value, and division by zero is undefined. Any increase from 0 would be infinitely large in percentage terms, so the tool shows the absolute change instead.