The Complementary Error Function is equal to 1  ERF (i.e. 1  Error Function), and is given by the equation:
Further information can be found on the Wikipedia Error Function pageThe Excel ERFC function calculates the Complementary Error Function, integrated between a supplied lower limit and infinity.
The format of the function is:
where x is the lower limit of the integral.
The Erfc function was improved in Excel 2010 in that it can now accept negative function arguments.
In Excel 2007 or earlier, if you input a negative value for the argument, x, the function would return an error. However, in Excel 2010, the function algorithm has been improved, so that it can now calculate the function for both positive and negative x values.
The spreadsheet below shows examples of the Excel Erfc function, used to calculate the Complementary Error Function integral for three different lower limits.
Formulas:
 Results:

Further examples of the Excel Erfc function are provided on the Microsoft Office website.
If you get an error from the Excel Erfc function this is likely to be one of the following:
#NUM!    Occurs older versions of Excel (Excel 2007 or earlier), if the supplied value of x is negative. 
#VALUE!    Occurs the supplied value of x is nonnumeric. 