Excel Formulas

What are number formats?

Whenever you're working with a spreadsheet, it's a good idea to use appropriate number formats for your data. Number formats tell your spreadsheet exactly what type of data you're using, such as percentages (%), currency ($), times, dates, and so on. For example, take a look at this spreadsheet, which uses a variety of number formats:

Why use number formats?

Number formats don't just make your spreadsheet easier to read—they also make it easier to use. When you apply a number format, you're telling your spreadsheet exactly what kinds of values are stored in a cell. For example, the date format tells the spreadsheet that you're entering specific calendar dates. This allows the spreadsheet to better understand your data, which can help ensure that your data remains consistent and that your formulas are calculated correctly.

If you don't need to use a specific number format, the spreadsheet will usually apply the general number format by default. However, the general format may apply some small formatting changes to your data.

Applying number formats

Just like other types of formatting, such as changing the font color, you'll apply number formats by selecting cells and then choosing the desired formatting option. Every spreadsheet program allows you to add number formatting, but the process will vary depending on which application you're using:

• For Microsoft Excel 2007-2013, go to the Home tab, click the Number Format drop-down menu in the Number group, and select the desired format. You can also click one of the quick number-formatting commands below the drop-down menu.
  

• For Excel 2003 and earlier, go to FormatCells.

• For Google Sheets, click the More Formats button near the left side of the toolbar—this button will look like the numbers 123. To the left of the command, you can also click the Currency or Percent commands to quickly apply those formats.

For most versions of Microsoft Excel, you can also select the desired cells and press Ctrl+1 on your keyboard to access more number-formatting options.

In this example, we've applied the Currency number format, which adds currency symbols ($) and displays two decimal places for any numerical values.

If you select any cells with number formatting, you can see the actual value of the cell in the formula bar. The spreadsheet will use this value for formulas and other calculations.

Using number formats correctly

There's more to number formatting than selecting cells and applying a format. Spreadsheets can actually apply a lot of number formatting automatically based on the way you enter data. This means you'll need to enter data in a way the program can understand, and then ensure that those cells are using the proper number format. For example, the image below shows how to use number formats correctly for dates, percentages, and times:

Now that you know more about how number formats work, we'll look at a few different number formats in action.

Percentage formats

One of the most helpful number formats is the percentage (%) format. It displays values as percentages, such as 20% or 55%. This is especially helpful when calculating things like the cost of sales tax or a tip. When you type a percent sign (%) after a number, the percentage number format will be be applied to that cell automatically.

As you may remember from math class, a percentage can also be written as a decimal. So 15% is the same thing as 0.15, 7.5% is 0.075, 20% is 0.20, 55% is 0.55, and so on. You can review this lesson from our Math tutorials to learn more about converting percentages to decimals.

There are many times when percentage formatting will be useful. For example, in the images below, notice how the sales tax rate is formatted differently for each spreadsheet (5, 5%, and 0.05):

As you can see, the calculation in the spreadsheet on the left didn't work correctly. Without the percentage number format, our spreadsheet thinks we want to multiply $22.50 by 5, not 5%. And while the spreadsheet on the right still works without percentage formatting, the spreadsheet in the middle is easier to read.

Date formats

Whenever you're working with dates, you'll want to use a date format to tell the spreadsheet that you're referring to specific calendar dates, such as July 15, 2014. Date formats also allow you to work with a powerful set of date functions that use time and date information to calculate an answer.

Spreadsheets don't understand information the same way a person would. For instance, if you type October into a cell, the spreadsheet won't know you're entering a date so it will treat it like any other text. Instead, when you enter a date, you'll need to use a specific format your spreadsheet understands, such as month/day/year (or day/month/year depending on which country you're in). In the example below, we'll type 10/12/2014 for October 12, 2014. Our spreadsheet will then automatically apply the date number format for the cell.

Now that we have our date correctly formatted, we can do lots of different things with this data. For example, we could use the fill handle to continue the dates through the column, so a different day appears in each cell:

If the date formatting isn't applied automatically, it means the spreadsheet did not understand the data you entered. In the example below, we've typed March 15th. The spreadsheet did not understand that we were referring to a date, so this cell is still using the general number format.

On the other hand, if we type March 15 (without the "th"), the spreadsheet will recognize it as a date. Since it doesn't include a year, the spreadsheet will automatically add the current year so the date will have all of the necessary information. We could also type the date several other ways, such as 3/15, 3/15/2014, or March 15 2014, and the spreadsheet would still recognize it as a date.

Other date-formatting options

Some programs have more date-formatting options, which can change the way dates appear in your spreadsheet. Again, this process this may vary slightly based on the spreadsheet program you're using. To access these options in Excel 2007-2013, select the Number Format drop-down menu and choose More Number Formats.

A dialog box will appear. From here, you can choose the desired date-formatting option.

As you can see in the formula bar, a custom date format doesn't change the actual date in our cell—it just changes the way it's displayed.

Number-formatting tips

Here are a few tips for getting the best results with number formatting:

• Apply number formatting to an entire column: If you're planning to use one column for a certain type of data, like dates or percentages, you may find it easiest to select the entire column by clicking the column letter and then applying the desired number formatting. This way, any data you add to this column in the future will already have the correct number format. Note that the header row usually won't be affected by number formatting.
  
• Double-check your values after applying number formatting: If you apply number formatting to existing data, you may have unexpected results. For example, applying percentage (%) formatting to a cell with a value of 5 will give you 500%, not 5%. In this case, you'd need to retype the values correctly in each cell.
  
  
  
• If you reference a cell with number formatting in a formula, the spreadsheet may automatically apply the same number formatting to the new cell. For example, if you use a value with currency formatting in a formula, the calculated value will also use the currency number format.
  
  
• If you want your data to appear exactly as enter it, you'll need to use the text number format. This format is especially good for numbers you don't want to perform calculations with, such as phone numbers, zip codes, or numbers that begin with 0: for example, "02415". For best results, you may want to apply the text number format before entering data in those cells.

To learn more about applying number formatting in a specific spreadsheet application, review the appropriate lesson from our tutorials below:

• Excel 2007-2013
• Excel 2003
• Google Sheets