How To Calculate Percent. Determine the total or whole amount. Divide the number to be expressed as a percent by the total. In most cases, you'll divide the smaller number by the larger number. Multiple the resulting value by 100. Example Percent Calculation. Say you have 30 marbles. Sometimes percentages can be frustrating because it’s not always easy to remember what we learned about them in school. Let Excel do the work for you – simple formulas can help you find the percentage of a total, for example, or the percentage difference between two numbers. Learn how to calculate percentages in this easy lesson! When you're asked to calculate an (unknown) percentage ('What percentage.?'), you need to first write the fraction PART/TOTAL, and then simply write that fraction as a decimal and as a percentage. See many examples in the lesson. What is the percentage? - How to find the percentage of something? Percentage is one of many ways to express a dimensionless ratio of two numbers. It's very popular since it can describe situations that involve large numbers (e.g., estimating chances for winning the lottery), average (e.g., determining final grade of your course) as well as very small ones (like volumetric proportion of NO₂. Free math lessons and math homework help from basic math to algebra, geometry and beyond. Students, teachers, parents, and everyone can find solutions to their math problems instantly. How to Calculate Percent Change Suppose the original price for a bag of apples is $3. On Tuesday, the bag of apples sells for $1.80. What is the percent decrease? Note that you would not find the difference between $3 and $1.80 yielding and answer of $1.20. If you know how to divide, multiply, add and subtract, you can quickly calculate sale discounts and other percentages taken off prices. This free percentage calculator computes a number of values involving percentages, including the percentage difference between two given values. Explore various other math calculators as well as hundreds of calculators addressing finance, health, fitness and more. Tips: Use tab to move to the next field. Use shift-tab to move to the previous field. Press enter to calculate. How to Calculate Percent Change. In mathematics, the concept of percent change is used to describe the relationship between an old value and new value. Specifically, the percent change expresses the difference between the old and new.