Microsoft Office Tutorials and References

In Depth Information

**Understanding text entries**

Excel can display values in many different formats. In the “Applying Number Formatting” section, later in this chapter,

you see how different format options can affect the display of numeric values.

Excel’s Numeric Limitations

You may be curious about the types of values that Excel can handle. In other words, how large can a

number be? And how accurate are large numbers?

Excel’s numbers are precise up to 15 digits. For example, if you enter a large value, such as

123,456,789,123,456,789 (18 digits), Excel actually stores it with only 15 digits of precision. This 18-digit

number displays as 123,456,789,123,456,000. This precision may seem quite limiting, but in practice,

it rarely causes any problems.

One situation in which the 15-digit accuracy can cause a problem is when entering credit card numbers.

Most credit card numbers are 16 digits, but Excel can handle only 15 digits, so it substitutes a zero

for the last credit card digit. Even worse, you may not even realize that Excel made the card number

invalid. The solution? Enter the credit card numbers as text. The easiest way is to preformat the cell as

Text (choose Home

Number and choose Text from the Number Format drop-down list). Or you can

precede the credit card number with an apostrophe. Either method prevents Excel from interpreting

the entry as a number.

➪

Here are some of Excel’s other numeric limits:

■
Largest positive number:
9.9E+3 07

■
Smallest negative number:
–9.9E+307

■
Smallest positive number:
1E–307

■
Largest negative number:
–1E–307

These numbers are expressed in scientiﬁ c notation. For example, the largest positive number is “9.9

times 10 to the 307th power” — in other words, 99 followed by 306 zeros. Keep in mind, though, that

this number has only 15 digits of accuracy.

Understanding text entries

Most worksheets also include text in some of the cells. Text can serve as data (for example,

a list of employee names), labels for values, headings for columns, or instructions about the

worksheet. Text is often used to clarify what the values in a worksheet mean or where the

numbers came from.

Text that begins with a number is still considered text. For example, if you type
12

Employees
into a cell, Excel considers the entry to be text rather than a numeric value.

Consequently, you can’t use this cell for numeric calculations. If you need to indicate that