Instantly calculate what X percent of Y is, find the percentage increase or decrease between two numbers, or work out a discount.
What is
%
of
?
100
Last updated: July 2026
The Easiest Way to Calculate Percentages
Whether you're trying to figure out a tip at a restaurant, checking your math homework, or trying to understand statistics in a news article, calculating percentages manually can be tricky. This tool covers three of the most common percentage calculations in one place — switch between the tabs above based on what you need.
Basic %: What Is X Percent of Y?
This is the most common percentage question: finding a portion of a number. The formula is (X ÷ 100) × Y. For example, 20% of 500 is (20 ÷ 100) × 500 = 100. This mode is useful for calculating tips, test scores, sales tax, or any time you need to know what a percentage of a total actually equals.
% Change: Finding an Increase or Decrease
Use this mode when you have two numbers and want to know how much something grew or shrank in percentage terms — like a price increase, a stock price move, or a change in a metric over time. The formula is ((New − Original) ÷ Original) × 100.
For example, going from 100 to 150 is a 50% increase, since (150 − 100) ÷ 100 × 100 = 50. Going the other direction, from 150 to 100, is a 33.3% decrease— notice the percentage isn't the same in both directions, because the base number you're dividing by changes.
Discount: Final Price and Savings
Enter an original price and a discount percentage to see exactly how much you'll save and what you'll actually pay. For example, a $100 item with a 15% discount saves you $15, bringing the final price to $85.
Common Uses for This Calculator
People use this tool to calculate restaurant tips, check test scores, work out sales tax, compare price increases between stores, calculate raise percentages, and figure out savings during a sale. Because all three modes are built into one calculator, you don't need to remember three different formulas — just pick the tab that matches your question.
Frequently Asked Questions
To find the percentage of a number, multiply the number by the percentage as a decimal. For example, to find 20% of 500, multiply 500 by 0.20 to get 100.
Percent literally means 'per hundred'. So 20 percent means 20 out of every 100.
Absolutely. If your bill is $45 and you want to leave a 20% tip, simply enter '20' and '45' into the Basic % mode to see that your tip should be $9.
Switch to the '% Change' tab and enter your starting and ending numbers. The calculator subtracts the two values, divides by the original number, and multiplies by 100 to give you the percentage change — labeled as an increase or decrease depending on the direction.
Percentage change = ((New Value − Original Value) / Original Value) × 100. A positive result means an increase; a negative result means a decrease.
Switch to the 'Discount' tab and enter the original price and the discount percentage. The calculator multiplies the price by the discount rate to find how much you save, then subtracts that from the original price to give you the final sale price.
A negative result means the value decreased rather than increased. For example, going from 150 to 100 is a decrease, so the calculator will show a negative percentage change (a 33.3% decrease) even though the 'Absolute difference' shown is a positive number.
Not currently — this tool calculates a percentage of a number, the percentage change between two numbers, and discounts. Averaging multiple percentages together is a different calculation and isn't supported in the current version.