The five percentage calculations people use most
Pick the tab that matches your question and type the numbers: the result appears instantly together with the formula used, so you can check it.
- What is X% of Y? Formula:
Y × X ÷ 100. Example: 15% of 200 is 30. - X is what % of Y? Formula:
X ÷ Y × 100. Example: 30 is 25% of 120. - X is P% of what number? Formula:
X ÷ (P ÷ 100). Example: if 30 is 25%, the total is 120. - Percentage change:
(final − starting) ÷ |starting| × 100. From 80 to 100 is up 25%; from 100 to 80 is down 20%. - Increase or decrease by %: handy for prices with tax or discounts. 100 plus 21% is 121.
Discounts and taxes
To take 30% off a price, use “Decrease” with 30%. To add a tax such as VAT or sales tax, use “Increase” with the tax rate. Remember that going up 25% and then down 25% doesn't bring you back to the start: the second step is applied to a different amount.
Need a ratio instead of a percentage? Try Proportion Calculator. To work out time spans, see Days Between Dates.
Frequently Asked Questions
How do I calculate the percentage of a number?
Multiply the number by the percentage and divide by 100. For example, 20% of 150 is 150 × 20 ÷ 100 = 30.
How do I calculate a discount?
Use “Increase / decrease by %” with the “Decrease” option. A 30% discount on 80 leaves the price at 56.
How do I find the percentage change between two values?
Subtract the starting value from the final one, divide by the starting value and multiply by 100. A negative result means a decrease.
Does it accept decimals and commas?
Yes. You can type 12.5 or 12,5; the calculator understands both formats.