How to Calculate Percentages on a Calculator

Whether you're working on your math homework or trying to leave a tip at a restaurant, a calculator can help you figure out the percentage of a number quickly and easily. Not sure how to do it? You’ve come to the right place! Finding percentages with a calculator is a piece of cake, and we talked to math tutor David Jia to show you how. From simply hitting that % button on your calculator to doing mental math, we have everything you need to know.

Using a Calculator: How to Do Percentages

To calculate a percentage on a calculator, enter a number and hit the % button to turn the number into a decimal. Alternatively, if you want to find the percentage of a number, multiply the number by the percentage as a fraction of 100 (e.g., to find 20% of 80, multiply 80 by 0.2).

Section 1 of 4:

Using the % Key on a Calculator

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1
Hit the % key to turn a percentage into a decimal. When you hit the % button on a calculator, the number will automatically turn into a decimal. For some calculators, you will see this action, on others, it’ll happen “behind the scenes.” This means you don’t have to do any mental math when doing a percentage conversion!
- Most calculators have a key with a % symbol; however, more advanced graphing calculators may not have this key readily available.
- Whenever you use a calculator for percentage calculations, make sure to press the Clear (C) or All Clear (AC) button before starting.
2
Try a practice problem to get more familiar with using the % key. Say you want to calculate a tip amount and find 15% of a $75.32 bill. Simply enter 15% x 75.32 into your calculator (don’t forget to hit the % button). You should get the result of 11.298, which represents a tip of $11.30.^{[1]
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- As you enter the numbers for this calculation, notice that as soon as you hit the % button, your number of 15 converts to .15. The calculator will then proceed to calculate .15 x 75.32.
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3
Experiment with the % key for decimal conversions. The simplest use of the % key on your calculator is to
convert any number from its percentage form to its decimal form.
Just enter the number and press the % button, and the calculator will show the decimal equivalent.
- To represent the number 4% on your calculator, press the button 4 and then %. Your calculator will turn the number 4 into 0.04, which is the decimal equivalent.
- To change the number 82.5% into a decimal, type the buttons 8, 2, . , 5, %. The calculator will now show the value of 0.825.

Section 2 of 4:

Calculating a Percentage of a Whole Number

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Convert the percentage into a decimal. When asked to find the percentage of something, Jia instructs to first convert the percentage into a decimal.^{[2]
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Expert Source

David Jia
Academic Tutor

Expert Interview. 7 January 2021.} To do this, simply divide the percentage by 100.^{[3]
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- For example, let’s say you’re at a restaurant and want to tip 15% of your $100 bill. Before finding how much you’ll tip, first turn 15% into a decimal by dividing 15 by 100. This will give you 0.15.
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David Jia
Math Tutor
David Jia is an Academic Tutor and the Founder of LA Math Tutoring, a private tutoring company based in Los Angeles, California. With over 10 years of teaching experience, David works with students of all ages and grades in various subjects, as well as college admissions counseling and test preparation for the SAT, ACT, ISEE, and more. After attaining a perfect 800 math score and a 690 English score on the SAT, David was awarded the Dickinson Scholarship from the University of Miami, where he graduated with a Bachelor’s degree in Business Administration. Additionally, David has worked as an instructor for online videos for textbook companies such as Larson Texts, Big Ideas Learning, and Big Ideas Math.

David Jia
Math Tutor

The word “percent” actually means “of 100.” A percentage is a special kind of fraction where the denominator is always set at 100. Because of this, when finding the “percentage of a number,” it can be helpful to remember that the word “percent” means “of 100,” with “per” meaning “of” and “cent” meaning “100.”
2
Replace the % with a multiplication sign. When working with percentages,
the word “of” carries the same meaning as “times” or “multiply.”
To find the percentage of a number, multiply the percentage decimal by the number. Therefore, 15% “of” 100, for example, means the same as 15% x 100 or 0.15 x 100.^{[4]
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- In our example, this means a 15% tip on a $100 bill is $15.
3
Write your result without a percentage symbol. When you set out to find a percentage of a whole number,
your result will be a number and not a percentage.
You may begin with a percentage symbol, but when you convert that percentage to a decimal, your answer will no longer have a percentage symbol.^{[5]
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- In the example of 15% of 100, the result is the whole number 15.

Section 3 of 4:

How to Do Basic Calculations with Percentages

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Add percentages as you would whole numbers. Because percentages all represent fractions with a common denominator of 100, you can add a list of percentages without any additional work. When adding, ignore the percent symbol and just add the numbers. Then, put the symbol back in your final answer.^{[6]
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- If each of six people draws a portion of the company’s payroll, you can find out how much they represent together by just adding the relative percentages. If their respective shares are 10%, 5%, 8%, 22%, 10%, and 8%, you can just add 10+5+8+22+10+8 = 63. Those six people make up 63% of the company’s payroll.
- By contrast, remember that to add fractions, you must work through finding common denominators and converting your fractions to those denominators.
2
Subtract percentages as if they were whole numbers. Again, because percentages represent fractions with a common denominator of 100, you do not need to do any additional work to subtract percentages. If you are removing some percentage from an original whole item, represent the whole item with the number 100 (because the whole means 100%).^{[7]
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- Suppose you want to calculate an income percentage. 100% represents the entire income from some project, but then you must subtract, for example, 10% for expenses, 12% for salaries, and 25% for taxes. How much is left? Simply use your calculator to perform the subtraction of 100-10-12-25. The result is 53%.
3
Multiply or divide using decimal equivalents. As Jia instructs, if you have a problem that is initially written as 25% x 30, just
write the 25% as its decimal equivalent 0.25 and conduct the operation.
This would be 0.25 x 30 which gives the result of 7.5.^{[8]
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Expert Source

David Jia
Academic Tutor

Expert Interview. 7 January 2021.}
- Similarly, if you have a division problem of 200 ÷ 10%, rewrite this as 200 ÷ 0.10 and enter this into your calculator. You will get the result of 2000.^{[9]
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- The last result may be surprising, but not every division result will be smaller than the original percentage. For example,
  dividing by 1/10 is the same as multiplying by 10.
  Dividing by 1/2 is the same as multiplying by 2.

Section 4 of 4:

How to Convert Fractions & Decimals to Percentages

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1
Use a calculator to convert any fraction to a decimal or percentage. If you are presented with any fraction, you can very easily convert it to a decimal number using a calculator. Think of the fraction as a division problem, and
use your calculator to divide the numerator by the denominator.
Your calculator will give you the decimal equivalent of the fraction.^{[10]
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- Suppose you have the fraction 1/2. On your calculator, perform the operation 1 ÷ 2, and the calculator will show the result 0.5.
- Convert the fraction 1/4 into a decimal by performing the operation 1 ÷ 4. The result is 0.25.
- For a more complicated example, you can convert the fraction 274/312 into a decimal with the operation 274 ÷ 312. The result will be 0.878. (There are more digits, but for our purposes, we can stop at three.)
2
Convert decimals to percentages by shifting the decimal point. If you have a number that is already represented by a decimal, converting that to a percentage is easy! Because the decimal numbering system is based on factors of 10, you can transform a decimal number into a percentage by simply
shifting the decimal point by two spaces to the right and adding a % sign at the end.
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- For example, 1/2 can be converted to the decimal of 0.5. Shift the decimal point two spaces to the right to change this decimal to a percentage. Rewrite 0.5 as 0.50. Then, when you shift the decimal point two spaces, you turn 0.50 into the number 50%.
- The example of 1/4, which has a decimal equivalent of 0.25, can be turned into the percentage 25%.
- If your decimal number consists of only one digit, you can add zeros on the right of the number, such as turning 0.5 into 0.50 or even 0.500. These all have the same numerical value.
$Step 3 Try memorizing basic fraction conversions to finish problems faster.$

3
Try memorizing basic fraction conversions to finish problems faster. Because the denominator for a percentage is always 100, certain values are constant. Some basic conversions you may want to know include:^{[12]
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- 3/4 = 75%
- 1/2 = 50%
- 1/3 = 33.33%
- 1/4 = 25%
- 1/5 = 20%
- 1/8 = 12.5%

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Question

How do you easily add the tip to a bill at a restaurant?

David Jia
Math Tutor
David Jia is an Academic Tutor and the Founder of LA Math Tutoring, a private tutoring company based in Los Angeles, California. With over 10 years of teaching experience, David works with students of all ages and grades in various subjects, as well as college admissions counseling and test preparation for the SAT, ACT, ISEE, and more. After attaining a perfect 800 math score and a 690 English score on the SAT, David was awarded the Dickinson Scholarship from the University of Miami, where he graduated with a Bachelor’s degree in Business Administration. Additionally, David has worked as an instructor for online videos for textbook companies such as Larson Texts, Big Ideas Learning, and Big Ideas Math.

David Jia

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Expert Answer

You can easily calculate your total bill including a tip or a tax by adding 1 to the percentage. For example, if you have a $20 meal and you want to add 15% to the bill, multiply $20 by 1.15 to get $23. That's faster than figuring out 15% of $20, which is $3, then adding it back to $20.

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Question

How do you take a percent of a number that isn't 100?

David Jia
Math Tutor
David Jia is an Academic Tutor and the Founder of LA Math Tutoring, a private tutoring company based in Los Angeles, California. With over 10 years of teaching experience, David works with students of all ages and grades in various subjects, as well as college admissions counseling and test preparation for the SAT, ACT, ISEE, and more. After attaining a perfect 800 math score and a 690 English score on the SAT, David was awarded the Dickinson Scholarship from the University of Miami, where he graduated with a Bachelor’s degree in Business Administration. Additionally, David has worked as an instructor for online videos for textbook companies such as Larson Texts, Big Ideas Learning, and Big Ideas Math.

David Jia

Math Tutor

Expert Answer

If you have a problem like "What's 25% of 50?" turn the percent into a decimal. In this case, 25% is the same as 0.25. Then, you'd multiply that by the second number—0.25 times 50, which is 12.5.

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What is 6% off 299.00?

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Multiply 299.00 by 0.06 to get the amount of the discount. Subtract that amount from 299.00 to find the number that replaces 299.00.

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