The Excel N function converts data into a numeric value, using the following rules :

The syntax of the function is:
where the value argument is the value that is to be converted, and can be supplied as either a direct value, a reference to a cell, or as the result of another formula.
The following spreadsheet shows several examples of the Excel N function. The formulas are shown in the spreadsheet on the left and the results are shown in the spreadsheet on the right.
Formulas:

Results:

Note that, in cells B3 of the above example spreadsheet, the date 01/01/2011 is converted to the serial number 40544. However, this serial number may differ on different computer systems.
Further information and examples of the Excel N function can be found on the Microsoft Office website.