Description
Each of these functions, referred to collectively as the IS functions, checks the specified value and returns TRUE or FALSE depending on the outcome. For example, the ISBLANK function returns the logical value TRUE if the value argument is a reference to an empty cell; otherwise it returns FALSE.
You can use an IS function to get information about a value before performing a calculation or other action with it. For example, you can use the ISERROR function in conjunction with the IF function to perform a different action if an error occurs:
= IF( ISERROR(A1), "An error occurred.", A1 * 2)
This formula checks to see if an error condition exists in A1. If so, the IF function returns the message "An error occurred." If no error exists, the IF function performs the calculation A1*2.
Syntax
ISBLANK(value)
ISERR(value)
ISERROR(value)
ISLOGICAL(value)
ISNA(value)
ISNONTEXT(value)
ISNUMBER(value)
ISREF(value)
ISTEXT(value)
The IS function syntax has the following argument:

value Required. The value that you want tested. The value argument can be a blank (empty cell), error, logical value, text, number, or reference value, or a name referring to any of these.
Function 
Returns TRUE if 
ISBLANK 
Value refers to an empty cell. 
ISERR 
Value refers to any error value except #N/A. 
ISERROR 
Value refers to any error value (#N/A, #VALUE!, #REF!, #DIV/0!, #NUM!, #NAME?, or #NULL!). 
ISLOGICAL 
Value refers to a logical value. 
ISNA 
Value refers to the #N/A (value not available) error value. 
ISNONTEXT 
Value refers to any item that is not text. (Note that this function returns TRUE if the value refers to a blank cell.) 
ISNUMBER 
Value refers to a number. 
ISREF 
Value refers to a reference. 
ISTEXT 
Value refers to text. 
Remarks

The value arguments of the IS functions are not converted. Any numeric values that are enclosed in double quotation marks are treated as text. For example, in most other functions where a number is required, the text value "19" is converted to the number 19. However, in the formula ISNUMBER("19"), "19" is not converted from a text value to a number value, and the ISNUMBER function returns FALSE.

The IS functions are useful in formulas for testing the outcome of a calculation. When combined with the IF function, these functions provide a method for locating errors in formulas (see the following examples).
Examples
Example 1
Copy the example data in the following table, and paste it in cell A1 of a new Excel worksheet. For formulas to show results, select them, press F2, and then press Enter. If you need to, you can adjust the column widths to see all the data.
Formula 
Description 
Result 
=ISLOGICAL(TRUE) 
Checks whether TRUE is a logical value 
TRUE 
=ISLOGICAL("TRUE") 
Checks whether "TRUE" is a logical value 
FALSE 
=ISNUMBER(4) 
Checks whether 4 is a number 
TRUE 
=ISREF(G8) 
Checks whether G8 is a valid reference 
TRUE 
=ISREF(XYZ1) 
Checks whether XYZ1 is a valid reference 
FALSE 
Example 2
Copy the example data in the following table, and paste it in cell A1 of a new Excel worksheet. For formulas to show results, select them, press F2, and then press Enter. If you need to, you can adjust the column widths to see all the data.
Data 

Gold 

Region1 

#REF! 

330.92 

#N/A 

Formula 
Description 
Result 
=ISBLANK(A2) 
Checks whether cell A2 is blank. 
FALSE 
=ISERROR(A4) 
Checks whether the value in cell A4, #REF!, is an error. 
TRUE 
=ISNA(A4) 
Checks whether the value in cell A4, #REF!, is the #N/A error. 
FALSE 
=ISNA(A6) 
Checks whether the value in cell A6, #N/A, is the #N/A error. 
TRUE 
=ISERR(A6) 
Checks whether the value in cell A6, #N/A, is an error. 
FALSE 
=ISNUMBER(A5) 
Checks whether the value in cell A5, 330.92, is a number. 
TRUE 
=ISTEXT(A3) 
Checks whether the value in cell A3, Region1, is text. 
TRUE 