# Count cells that contain errors

=SUMPRODUCT(--ISERROR(range))

To count cells that contain errors, you can use the ISERROR function, wrapped in the SUMPRODUCT function. In the example shown, E5 cell contains this formula:

=SUMPRODUCT(--ISERROR(B5:B9))

The SUMPRODUCT function accepts one or more arrays, multiplies the arrays together, and returns the "sum of products" as a final result. If only one array is supplied, SUMPRODUCT simply returns the sum of items in the array.

In the example shown, the goal is to count errors in a given range. The formula in E5 is:

=SUMPRODUCT(--ISERROR(B5:B9))

Working from the inside out, the ISERROR function returns TRUE when a cell contains an error, and FALSE if not. Because there are five cells in the range B5:B9, ISERROR evaluates each cell and returns five results in an array like this:

{TRUE;FALSE;TRUE;FALSE;TRUE}

To coerce the TRUE/FALSE values to 1's and 0's, we use a double negative (--). The resulting array looks like this:

{1;0;1;0;1}

Finally, SUMPRODUCT sums the items in this array and returns the total, which is 3 in this case.

### ISERR option

The ISERROR function counts *all* errors. If for some reason you want to count all errors *except* #N/A, you can use the ISERR function instead:

=SUMPRODUCT(--ISERR(B5:B9)) // returns 2

Since one of the errors shown in the example is #N/A, the ISERR option returns 2 instead of 3.

### Array formula with SUM

You can also use the SUM function to count errors, but you must enter as an array formula. Once entered the formula will look like this:

The curly brackets are added automatically by Excel and indicate an array formula.

*Note: this is an array formula, and must be entered with control + shift + enter, except in Excel 365.*

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