=COUNTBLANK(range)
=COUNTBLANK(B5:B15)
The COUNTBLANK Function can be used to count the number of blank cells in a range. For example, will return the number of blank cells in the range from cell B5 to B15.
=IF(A1>30,"Overdue","")
COUNTBLANK will also count empty strings as blank cells. For example, if the formula returns an empty string, COUNTBLANK will count this as a blank cell.
The COUNTBLANK function is used in Sourcetable to count the number of empty cells in a range of cells. It also counts cells with formulas that return "", though it does not count those with zero values.