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Let's say you want to calculate a sales tax for different states, compute a grade for a test score, or determine a percent change in sales between two fiscal quarters. There are several ways to calculate percentages.
Percentages are calculated by using the following equation:
amount/total = percentage
Where percentage is in decimal format.
To quickly display the result as a percentage, Click Percent Style on the Formatting toolbar.
What do you want to do?
Calculate the amount if you know the total and percentage
Calculate the percentage if you know the total and amount
Calculate the total if you know the amount and percentage
Calculate the difference between two numbers as a percentage
Increase or decrease a number by a percentage
Calculate the amount if you know the total and percentage
For example, if you purchase a computer for $800 and there is an 8.9% sales tax, how much do you have to pay for the sales tax? In this example, you want to find 8.9% of 800.
Example
The example may be easier to understand if you copy it to a blank worksheet.
How to copy an example
 Create a blank workbook or worksheet.
 Select the example in the Help topic.
Note Do not select the row or column headers.
Selecting an example from Help
 Press CTRL+C.
 In the worksheet, select cell A1, and press CTRL+V.
 To switch between viewing the results and viewing the formulas that return the results, press CTRL+` (grave accent), or on the Tools menu, point to Formula Auditing, and then click Formula Auditing Mode.

A 
B 
Purchase price 
Sales tax (in decimal form) 
800 
0.089 
Formula 
Description (Result) 
=A2*B2 
Multiplies 800 by 0.089 to find the amount of sales tax to pay ($71.20) 

Note To convert a number in percentage format to a decimal, divide it by 100. For example, the sales tax in this example (8.9) divided by 100 is .089.
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Calculate the percentage if you know the total and amount
For example, if you score 42 points correctly out of 50, what is the percentage of correct answers?
Example
The example may be easier to understand if you copy it to a blank worksheet.
How to copy an example
 Create a blank workbook or worksheet.
 Select the example in the Help topic.
Note Do not select the row or column headers.
Selecting an example from Help
 Press CTRL+C.
 In the worksheet, select cell A1, and press CTRL+V.
 To switch between viewing the results and viewing the formulas that return the results, press CTRL+` (grave accent), or on the Tools menu, point to Formula Auditing, and then click Formula Auditing Mode.

A 
B 
Points answered correctly 
Total points possible 
42 
50 
Formula 
Description (Result) 
=A2/B2 
Divides 42 by 50 to find the percentage of correct answers (0.84 or 84%) 

Note To display the number as a percentage, select the cell and then click Percent Style on the Formatting toolbar.
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Calculate the total if you know the amount and percentage
For example, the sale price of a shirt is $15, which is 25% off the original price. What is the original price? In this example, you want to find 75% of which number equals 15.
Example
The example may be easier to understand if you copy it to a blank worksheet.
How to copy an example
 Create a blank workbook or worksheet.
 Select the example in the Help topic.
Note Do not select the row or column headers.
Selecting an example from Help
 Press CTRL+C.
 In the worksheet, select cell A1, and press CTRL+V.
 To switch between viewing the results and viewing the formulas that return the results, press CTRL+` (grave accent), or on the Tools menu, point to Formula Auditing, and then click Formula Auditing Mode.

A 
B 
Sale price 
100% minus the discount (in decimal form) 
15 
0.75 
Formula 
Description (Result) 
=A2/B2 
Divides 15 by 0.75 to find the original price (20) 

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Calculate the difference between two numbers as a percentage
For example, your earnings are $2,342 in November and $2,500 in December. What is the percentage change in your earnings between these two months? To do this task, use the ABS function and the subtraction () and division (/) operators.
Example
The example may be easier to understand if you copy it to a blank worksheet.
How to copy an example
 Create a blank workbook or worksheet.
 Select the example in the Help topic.
Note Do not select the row or column headers.
Selecting an example from Help
 Press CTRL+C.
 In the worksheet, select cell A1, and press CTRL+V.
 To switch between viewing the results and viewing the formulas that return the results, press CTRL+` (grave accent), or on the Tools menu, point to Formula Auditing, and then click Formula Auditing Mode.

A 
B 
November earnings 
December earnings 
2342 
2500 
Formula 
Description (Result) 
=(B2A2)/ABS(A2) 
Divides the difference between the second and first numbers by the absolute value of the first number to get the percentage change (0.06746 or 6.75%) 

Note To display the number as a percentage, select the cell and then click Percent Style on the Formatting toolbar.
Function details
ABS
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Increase or decrease a number by a percentage
For example, you spend an average of $25 on food each week, and you want to cut your weekly food expenditures by 25%. How much can you spend? Or, if you want to increase your weekly food allowance of $25 by 25%, what is your new weekly allowance?
Example
The example may be easier to understand if you copy it to a blank worksheet.
How to copy an example
 Create a blank workbook or worksheet.
 Select the example in the Help topic.
Note Do not select the row or column headers.
Selecting an example from Help
 Press CTRL+C.
 In the worksheet, select cell A1, and press CTRL+V.
 To switch between viewing the results and viewing the formulas that return the results, press CTRL+` (grave accent), or on the Tools menu, point to Formula Auditing, and then click Formula Auditing Mode.

A 
B 
Number 
Percentage 
25 
25% 
Formula 
Description (Result) 
=A2*(1B2) 
Decreases 25 by 25% (18.75) 
=A2*(1+B2) 
Increases 25 by 25% (31.75) 
=A2*(1+35%) 
Increases 25 by 35% (33.75) 

Note When you type a number followed by a percent sign (%), the number is interpreted as a hundredth of its value. For example, 5% is interpreted as .05.
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