ISERROR Function in Excel: What It Does and How to Use It

In Excel, ISERROR checks whether a value or formula result is any error value, and returns TRUE if it is or FALSE if it is not. It is useful for detecting errors in cells and controlling what a workbook displays when a calculation or lookup fails.

What the ISERROR Function Does

ISERROR is an information function: it reports something about a value rather than changing that value. If the value being checked is an Excel error, the function returns the logical value TRUE. For a regular number, text string, date, blank-cell reference, or other non-error value, it returns FALSE.

That distinction makes the function helpful in worksheets where errors are expected possibilities. A lookup might not find a match, a calculation might divide by zero, or a reference might point to a deleted cell. Instead of assuming every cell contains a usable result, a formula can test for an error and respond accordingly.

ISERROR does not repair an error or explain its cause. It only identifies whether the value supplied to it is an error. The result is a Boolean value—TRUE or FALSE—which you can use in another formula, display directly, or use as a condition in a check.

Syntax and Basic Use

The function has one argument, shown in Excel’s standard syntax as ISERROR(value). The argument can be a cell reference, a named range, a calculation, or another formula that produces a value. You can enter it directly in a worksheet cell or use it inside a larger formula.

With an error value in A2, enter =ISERROR(A2) in B2. B2 displays TRUE when A2 contains an error and FALSE otherwise. The same check can be made on an expression rather than a cell: =ISERROR(1/0) returns TRUE, because dividing by zero produces #DIV/0!.

In Microsoft Excel for Microsoft 365 on Windows, type the formula into a cell and press Enter. Excel normally uses commas between arguments in formulas, though regional settings can use semicolons instead. The syntax and behavior are the same in Excel for Mac and Excel for the web; the main difference is the interface, not this function.

Which Errors It Detects

ISERROR is broad: it returns TRUE for any Excel error value, not just one particular kind. Common examples include:

#DIV/0!, often caused by dividing by zero or by a blank denominator.
#N/A, commonly returned when a lookup cannot find a match.
#VALUE!, which can occur when a formula receives an unsuitable type of value.
#REF!, which indicates an invalid cell reference.
#NAME?, which can result from an unrecognized function or name.
#NUM! and #NULL!, which indicate other kinds of invalid calculation or reference.

It also detects newer errors that can appear in Microsoft 365, such as #SPILL! or #CALC!, when those errors are produced by a feature or formula in the workbook. The precise errors a workbook can generate depend on its formulas and the Excel features it uses.

A cell that displays the characters #N/A as ordinary text is not the same as a cell containing the actual #N/A error. ISERROR returns FALSE for text that merely looks like an error. This matters when data has been imported from another system: a visual match does not prove that Excel sees an error value.

Practical Examples

A direct check can identify which rows contain errors. Suppose column A contains formulas or values and you want a status beside each one. With the value to inspect in A2, enter this in B2 and fill it down: =ISERROR(A2). Each row will show TRUE or FALSE, making it possible to filter or review the flagged rows.

You can also test a calculation before deciding what to show. With a numerator in A2 and a denominator in B2, this formula in C2 returns a warning when the division produces an error and the quotient otherwise: =IF(ISERROR(A2/B2),"Check values",A2/B2). If A2 contains 12 and B2 contains 0, the result is Check values. If A2 is 12 and B2 is 3, the result is 4.

That pattern works, but it calculates the division expression twice: once for the test and once for the result when there is no error. Excel’s IFERROR function is often simpler for this specific job. With the same numerator and denominator in A2 and B2, use =IFERROR(A2/B2,"Check values") in C2. It returns the quotient when the calculation succeeds and the replacement text when it returns an error.

To count errors in a range, you can combine ISERROR with SUMPRODUCT. With values or formulas in A2:A20, enter =SUMPRODUCT(--ISERROR(A2:A20)) in another cell. It returns the number of cells in that range whose values are errors. For example, if three cells contain errors and the rest do not, the result is 3. The double unary operator converts the TRUE/FALSE results into 1s and 0s so they can be added.

Using ISERROR to Control What a Worksheet Shows

One common use is to keep an error from appearing in a report. The test can be paired with IF to show a message, a blank, or another value when an error occurs. With a calculation in A2, for example, =IF(ISERROR(A2),"",A2) displays a blank if A2 contains an error and otherwise repeats A2’s value.

Hiding errors may make a summary easier to read, but it can also make a problem less visible. A blank might mean “not applicable,” “not yet calculated,” or “calculation failed,” and those meanings are not interchangeable. For workbooks used by other people, a clear message such as “Check input” can be more informative than an empty cell.

Use a targeted message when the cause is known. For instance, if a formula divides one input by another, a zero denominator can be handled directly with an IF test, while other errors can be left visible for investigation. A broad ISERROR test is appropriate when the goal is to catch any error, but it does not tell you which error occurred or whether the underlying data is sensible.

ISERROR, ISERR, ISNA, and IFERROR Compared

These similarly named functions serve different purposes. Choosing one depends on whether you need to identify an error, catch a particular type, or substitute a result.

ISERROR(value) returns TRUE for any error value, including #N/A.
ISERR(value) returns TRUE for errors other than #N/A. It is useful when a missing lookup match should be treated differently from other failures.
ISNA(value) returns TRUE only for the #N/A error. It is a focused test for unavailable or unmatched results.
IFERROR(value, value_if_error) returns a chosen replacement when its first argument is any error; otherwise, it returns the first argument’s result.
IFNA(value, value_if_na) substitutes a result only for #N/A, leaving other errors visible.

A key difference is that ISERROR returns a logical test result, while IFERROR returns either the original calculation’s result or a replacement. Use ISERROR when you need a TRUE/FALSE flag or when a formula needs to make a decision based on whether an error occurred. Use IFERROR when you simply want a fallback value. If only missing matches should be handled, IFNA is usually more precise than suppressing every possible error.

Common Problems and Misconceptions

Thinking it fixes the source error: It does not. A TRUE result tells you that the supplied value is an error; it does not correct a bad reference, missing input, or invalid calculation. Fixing the formula or data may be preferable to masking the result.

Expecting it to recognize error-looking text: The text #DIV/0! stored as text is not an error value, so the test returns FALSE. If imported data may contain error labels as text, you need to check the text itself using an appropriate text comparison rather than relying on ISERROR.

Using it where a narrower test is needed: Because it catches every error, ISERROR can hide an unexpected #REF! or #VALUE! along with an ordinary missing-match #N/A. That can make troubleshooting harder. Match the test or fallback function to the condition you actually intend to handle.

Misreading TRUE and FALSE: Those are logical values, not the text strings “TRUE” and “FALSE.” They can be used directly in logical tests and calculations. If a sheet needs a custom label, wrap the test in IF and provide the desired text.

Checking the wrong cell: A formula may return a normal-looking value even when an upstream calculation has a problem, or an error may arise only when several cells are combined. Test the expression or result that matters to the decision, not just a nearby input cell.

Frequently Asked Questions

Does ISERROR detect #N/A?
Yes. ISERROR detects #N/A as well as other Excel error values. Use ISNA if you want a test that returns TRUE only for #N/A.

What does ISERROR return if the cell is blank?
If the argument is a reference to a genuinely blank cell, ISERROR returns FALSE. A blank is not itself an Excel error, though a formula that uses that blank could still produce an error in some calculations.

Can ISERROR hide an error from users?
Not by itself: it returns TRUE or FALSE. Combined with IF, it can display a different value or message instead of the error. Consider whether that replacement could conceal a problem someone needs to investigate.

What is the difference between ISERROR and IFERROR?
ISERROR reports whether a value is an error by returning TRUE or FALSE. IFERROR returns the original result when there is no error and a specified fallback when there is one.

Does ISERROR work in Excel for Mac or the web?
Yes. The function is available in Excel for Microsoft 365 on Windows, Excel for Mac, and Excel for the web. The formula behavior is the same, although the menus and interface differ between platforms.

When ISERROR Is the Right Choice

Choose ISERROR when you need a general error check: to flag problematic cells, count errors, or make a formula branch based on whether a calculation failed. If the goal is only to supply a fallback result, IFERROR is usually more direct; if you only care about #N/A, consider ISNA or IFNA. Keeping that distinction in mind makes error handling clearer and reduces the risk of hiding a different problem by accident.

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Sources: Function behaviour and menu paths: Microsoft Support documentation for Excel. Method & sources

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