ToolPercentage Calculator
Six quick calculators in one: percent of a number, what percent one number is of another, percentage change, add or subtract a percentage, and finding the whole from a part.
How to calculate a percentage
- Find the card that matches your question, such as “What is X% of Y?” or “Percentage change”.
- Type your two numbers. The answer updates as you type.
- Use the formula shown with each result to check it or repeat it on paper.
Percentage formulas, in plain words
A percentage is a number out of 100. To find X% of Y, multiply Y by X and divide by 100: 15% of 2,400 is 2,400 × 15 ÷ 100 = 360. To find what percent X is of Y, divide X by Y and multiply by 100: 45 out of 180 is 25%.
Percentage change compares a new value with the old one: subtract old from new, divide by the old value, and multiply by 100. From 80 to 100 is +25%; from 100 back to 80 is −20%, because the base changed.
Discounts, GST and VAT
To take a discount, use “Subtract X% from Y”: a 25% discount on 2,000 leaves 1,500. To add tax, use “Add X% to Y”: 18% GST on 1,000 makes 1,180. To work out the pre-tax price from a tax-inclusive total, divide by 1 + rate (for 18% GST, divide by 1.18), or use the dedicated GST calculator or UAE VAT calculator.
Common percentage mistakes
- Increase then decrease by the same percent does not return to the start. +20% then −20% of 100 gives 96, not 100.
- Percentage points are not percent. Going from 10% to 12% is +2 percentage points but a 20% increase.
- The base matters. “X% of Y” and “Y% of X” are equal numbers, but “what percent” and “percentage change” depend on which number you divide by.
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 2,400 = 2,400 × 15 ÷ 100 = 360. The first calculator does this automatically.
How do I calculate percentage increase or decrease?
Subtract the old value from the new value, divide by the old value and multiply by 100. A positive result is an increase and a negative result is a decrease. Use the “Percentage change” calculator.
How do I add or remove a percentage like GST?
To add a percentage, multiply by 1 + rate (for 18%: × 1.18). To remove it, divide by the same factor. The “Add or subtract” card shows both results at once.
Why is a 20% rise followed by a 20% fall not the same as the start?
Each percentage applies to a different base. A 20% rise on 100 gives 120, and 20% of 120 is 24, so the fall leaves 96.
Is this percentage calculator free and private?
Yes. It is free, needs no signup, and calculates entirely in your browser.