ISBLANK Function

The ISBLANK function returns TRUE when a cell is empty, and FALSE when a cell is not empty. For example, if A1 contains "apple", ISBLANK(A1) returns FALSE. Use the ISBLANK function to test if a cell is empty or not. ISBLANK function takes one argument, value, which is a cell reference like A1.

The word "blank" is somewhat misleading in Excel, because a cell that contains only space will look blank but not be empty. In general, it is best to think of ISBLANK to mean "is empty" since it will return FALSE when a cell looks blank but is not empty. 

Examples

If cell A1 contains nothing at all, the ISBLANK function will return TRUE:

=ISBLANK(A1) // returns TRUE

If cell A1 contains any value, or any formula, the ISBLANK function will return FALSE:

=ISBLANK(A1) // returns false

Is not blank

To test if a cell is not blank, nest ISBLANK inside the NOT function like this:

=NOT(ISBLANK(A1)) // test not blank

The above formula will return TRUE when a cell is not empty, and FALSE when a cell is empty.

Empty string syntax

Many formulas will use an abbreviated syntax to test for empty cells, instead of the ISBLANK function. This syntax uses an empty string ("") with Excel's math operators "=" or "<>". For example, to test if A1 is empty, you can use:

=A1="" // TRUE if A1 is empty

To test if A1 is not empty:

=A1<>"" // TRUE if A1 is not empty

This syntax can be used interchangeably with ISBLANK. For example, inside the IF function:

=IF(ISBLANK(A1),result1,result2) // if A1 is empty

is equivalent to:

=IF(A1="",result1,result2) // if A1 is empty

Likewise, the formula:

=IF(NOT(ISBLANK(A1)),result1,result2)

is the same, as:

=IF(A1<>"",result1,result2)

Both will return result1 when A1 is not empty, and result2 when A1 is empty.

Empty strings

If a cell contains any formula, the ISBLANK function and the alternatives above will return FALSE, even if the formula returns an empty string (""). This can cause problems when the goal is to count or process blank cells that include empty strings.

One workaround is to use the LEN function to test for a length of zero. For example, the formula below will return TRUE if A1 is empty or contains a formula that returns an empty string:

=LEN(A1)=0 // TRUE if empty

So, inside the IF function, you can use LEN like this:

=IF(LEN(A1)=0,result1,result2) // if A1 is empty

You can use this same approach to count cells that are not blank.