How to Figure Out Percentages

By Hannah Richardson; Updated April 24, 2017
Money is a real world example of why you would need to figure out percentages

To figure out a percentage, turn the percentage into a decimal, then multiply the decimal value by the total. To turn a percentage into a decimal, move the original decimal two places to the left. If your percentage is a whole number without a visible decimal, this invisible decimal is located at the end of the number. For example, 123 percent has an invisible decimal after the 3, so when you move it two places to the left, your decimal value is 1.23. You can use this process to find percentages not only in the classroom, but in real world percentage problems, as well. Use this process to find the amount for a tip at a restaurant, or to find the amount of a discount when shopping, or to figure out an increase in profits for a business.

To figure out a tip at a restaurant, convert your percentage to a decimal and multiply it by your total bill. Your answer is the tip amount. For example, to figure out an 18 percent tip on a $32.74 bill, first convert 18 percent to .18. Multiply .18 and 32.74, and you will get a total value of 5.8932. Because money is only two decimal points, this tip will round to $5.89. To find the total bill, add $5.89 to $32.74. The total you will pay is $38.63.

To figure out a discount price, you will not only have to turn the percent into a decimal and multiply that decimal by the original price, but you will then need to subtract that percentage from the original price. For example, if you want to buy a pair of jeans that are $99 but are on sale for 30 percent off, first turn 30 percent to .3. Multiply .3 and 99 to get 29.7. Your discount will be $29.70. To find the sale price, subtract $29.70 from $99, and what you will actual pay at the register is $69.30.

To find a percentage change, such as a business' increase in profits from one quarter to the next, you will need to find the difference first, and then convert a decimal into a percent. First, calculate the change by subtracting the smaller number from the larger number. Then, divide the change by the original number. You answer will be a decimal, so you will have to change this decimal into a percentage by moving the decimal two places to the right. For example, if a business grossed $158,000 in the first quarter and $173,000 in the second quarter, find the difference. Subtract $158,000 from $173,000. Divide this change, $15,000 by the original, $158,000. Your decimal value will be 0.094936709. After moving the decimal two places to the right, your full percentage will be 9.4936709. You could also round this to 9.49 percent.

Tip

If you are rounding a long decimal number to a money value, remember you are looking at the third number to figure out whether the second number will stay the same or round up. If the third number is five or above, round the second decimal up one.

If your answer has only one digit to left of the decimal, add a zero if your answer is money. For example, if you find that 60 percent of $38 is 22.8, you will still need two decimal places because your answer is money. Add a zero to change 22.8 into $22.80.

If your calculator has a percentage (%) button, you can type it into your multiplication problem exactly as you see it: 70 percent. For example, to find 70 percent of $45, you would type in 70% x 45 for a total of $31.50.

Warning

Make sure that when you are converting a decimal to a percent, you move the decimal two places to the right. You are making the number bigger.

Make sure that when you are converting a percent to a decimal, you move the decimal two places to the left: no more or less.

About the Author

Hannah Richardson has a Master's degree in Special Education from Vanderbilt University and a Bacheor of Arts in English. She has been a writer since 2004 and wrote regularly for the sports and features sections of "The Technician" newspaper, as well as "Coastwach" magazine. Richardson also served as the co-editor-in-chief of "Windhover," an award-winning literary and arts magazine. She is currently teaching at a middle school.