Excel: IsErr Function
In Excel, the IsErr function can be used to check for error values.
The syntax for the IsErr function is:
IsErr( value )
value is the value that you want to test. If value is an error value (except #N/A), this function will return TRUE. Otherwise, it will return FALSE.
Applies To:
- Excel 2007, Excel 2003, Excel XP, Excel 2000
For example:
Let's take a look at an example:

Based on the Excel spreadsheet above:
=IsErr(A1) would return TRUE. =IsErr(A2) would return FALSE. =IsErr(A3) would return TRUE. =IsErr(A4) would return FALSE. =IsErr("Tech on the Net") would return FALSE. =IsErr(3/0) would return TRUE.
Frequently Asked Questions
Question: Can you give me specific examples of when and how the IsErr function is used. Specifically, in a worksheet why would I use this function instead of just running down a column or across a row to look for the errors?
Answer: Often times your spreadsheet contains a large amount of formulas which will not properly calculate when an error is encountered. The IsErr function, in combination with the If function, can be used to default a cell's value when an error is occurred. This allows your formulas to evaluate properly without your intervention.
For example, you may encounter a scenario below:

Instead of using the formula:
=B4/C4
You could use the IsErr function as follows:
=IF(ISERR(B4/C4),0,B4/C4)

In this case, the IsErr function would allow you to return a 0, when an error was encounter such as a "divide by 0 error". Now all of your formulas will still work.