Easy Way to Do Percentages Without a Calculator

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A percentage is a special way of representing a portion of something. A percentage is a number that indicates a fraction made up of 100 parts. Thus, 100% means the whole thing (whatever is being measured), while 50% means one half. If you learn how to write numbers as percentages, it then becomes easy to perform multiplication and other calculations with percentages on a calculator. Some calculators even have a % button that makes the calculation even easier.

1. 1

   Review the general meaning of fractions. A fraction is a comparison between two numbers, usually representing the size of a part of something to the size of the whole thing. The classic example is a pie that is cut into eight, for example, equal portions. The top of the fraction, called the

   numerator, represents the number of pieces you select.

   The bottom of the fraction, called the

   denominator, represents the total number of pieces in the pie

   - in this case, 8.^[1]

   • For example, the fraction 1/8 represents one piece of the pie that has been cut in eight pieces.
   • The fraction 7/8 represents 7 pieces, almost the full pie.

2. 2

   Recognize the special relationship of percentages. A percentage is a special kind of fraction in which the

   denominator is always set at 100.

   ^[2] While this is not practical when cutting slices of an actual pie, the concept of percentages is much more useful because it is standard.

   • With fractions, the size of "half" of something will depend on the number of pieces. If your "pie" is cut into 8 pieces, then half would be 4. But if your "pie" is in 22 pieces, then half would be 11. The target always changes. But with percentages, one-half is always the same - 50%.
   • It's helpful to remember that the word "percent" actually means "of 100"—"per" means "of," and "cent" means "100."^[3]

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3. 3

   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 any calculator. Just recognize that a fraction represents 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.^[4]

   • 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.)

4. 4

   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 then adding a % sign.

   If your decimal number consists of only one digit, you can add 0's 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.^[5]

   • Consider the example above of 1/2, which we converted to the decimal of 0.5. To change this decimal to a percentage, shift the decimal point two spaces to the right. First 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%.

5. 5

   Memorize basic fraction conversions. It is useful if you can memorize the percentage representations of certain basic fractions. Because the denominator for a percentage is always 100, certain values are constant. Some basic conversions you should know include:^[6]

   • 3/4 = 75%
   • 1/2 = 50%
   • 1/3 = 33 1/3%
   • 1/4 = 25%
   • 1/5 = 20%
   • 1/8 = 12.5% (this is often used in banking)

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1. 1

   Add percentages very directly. Because percentages all represent fractions with the common denominator of 100, you can add a list of percentages without any additional work. By contrast, remember that to add fractions, you must work through the steps of finding common denominators and converting your fractions to those common denominators. With percentages, however, no additional work is necessary.

   Just add the numbers together.

   • 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.
   • When you are adding, ignore the percent symbol, and just add the numbers. Put the symbol back in your final answer.

2. 2

   Subtract percentages in the same manner. Again, because percentages represent fractions with the common denominator of 100, you do not need to do any additional work to subtract percentages. If you are working the the concept of removing some percentage from an original whole item, you should represent the whole item with the number 100 (because the whole means 100%).

   • 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. 3

   Multiply or divide using decimal equivalents. 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. ^[7] 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.^[8]

   • The last result may appear surprising, if you expect division to produce a smaller result than the starting number. However, you should understand that division by a number less than one will always lead to an increase by the reciprocal of that number. For example,

     dividing by 1/10 is the same as multiplying by 10.

     Dividing by 1/2 is the same as multiplying by 2.

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1. 1

   Perform multiplication to find the percent "of" a number. A common calculation involving percentages is to find some percent "of" another number. For example, if you are in a restaurant you may want to tip 15% "of" your total bill. When working with percentages,

   the word "of" carries the same meaning as "times" or "multiply."

   Therefore, 15% "of" 100, for example, means the same as 15% x 100.^[9]

2. 2

   Convert the percentage to a decimal and multiply. To calculate the percentage of the whole number, you need to first turn the percentage into a decimal as already described. Then simply multiply.^[10]

   • To find 15% of 100, rewrite the 15% as 0.15. Then just multiply 0.15 x 100, to get the solution of 15.

3. 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 to conduct the multiplication, your answer will no longer have a percentage symbol.

   • In the example of 15% of 100, the result is the whole number 15.

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1. 1

   Find the % key on your calculator. Most simple calculators will contain a key with the % symbol. More advanced, graphing calculators may not have this key because the makers expect that you can operate without it. But many more basic calculators will have it.

2. 2

   Experiment with the % key for decimal conversions. The simplest use of the % key 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, just 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, just type the buttons 8, 2, . , 5, %. The calculator will now show the value of 0.825.

3. 3

   Use the % key for calculations. The % key on your calculator makes certain calculations very simple. Suppose you want to calculate a tip amount, and you want to find 15% of the total bill of $75.32. If you have your calculator available, you will enter the buttons 15% x 75.32. You should get the result of 11.298, which represents a tip of $11.30.

   • Whenever you are using a calculator for percentage calculations, you should make sure to press the Clear (C) or All Clear (AC) button before starting.
   • As you enter the numbers for this calculation, you should notice that as soon as your hit the % button, your number of 15 converts to .15. The calculator will the proceed to calculate .15 x 75.32.

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• Question

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

  

  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.

  

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  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.

• Question

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

  

  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.

  

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  Support wikiHow by unlocking this 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.

• Question

  What is 6% off 299.00?

  

  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.

• Question

  164 selections, 46 winners. What is the percentage?

  

  If you're asking what percentage 46 is of 164, divide 46 by 164, multiply the quotient by 100, and place a percent sign to the right.

• Question

  How do I get a percentage when it's 19/29?

  

  Divide 19 by 29, then multiply the quotient by 100, and add the % mark.

• Question

  What percentage is 62,000,000 of 163,433,400?

  

  Divide the first number by the second, then multiply by 100 (and add the % mark).

• Question

  How do I work out 15% when my mobile phone calculator has no % key?

  

  Multiply by 0.15.

• Question

  If I'm getting a pay increase of 2.05%, how do I figure that?

  

  Multiply the original pay amount by 0.0205. That gives you the pay increase. Add that to the original pay amount to find the new pay amount.

• Question

  How do I convert a number to a percentage of another number?

  

  To convert 2 to a percentage of 4, for example, first divide 2 by 4. The answer is a decimal. Multiply it by 100, then add the percent sign.

• Question

  How do I figure the percentage increase of 282,152 - 277,088 = 5064?

  

  Divide the difference (5,064) by the original number (277,088).

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Article Summary X

To do percentages on a calculator using the percentage button, enter the percentage times the original number. For example, if you wanted to give a waiter a 20% tip on your $50 order, you would enter 20 and hit the percentage button to get 20%. Then you would hit the multiplication button, enter 50, and hit the equals button to find that 20% of $50 is $10. Read more to learn how to find percentages without using the percentage button!

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