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Excel WEEKNUM Function

Want to learn more about how to returns the week number of a specific date using excel spreadsheet?? This post will give you an overview of how to get the week number of any date in excel.

Syntax(Generic Formula)

=WEEKNUM(serial_num, [return_type])

  • Serial_num [Required]It is an excel date for which we want to return the week number for.
  • return_type  [optional] – A number that shows the first day of the week for the year. By Default is 1.

How the WEEKNUM function Works

The WEEKNUM function is a built-in categorized Date/Time function in Excel. The function will return week number between from 1 to 52.

Figure 1: Example of returns the week number of a specific date

To find the year corresponding to a date, the WEEKNUM you can use the function. In the example selected cell shown, the formula in C5 is:


If serial_number is not in range for the current date base value, a #NUM! the error is returned. If return_type is out of the range in the table then, a #NUM! the error is returned.

Two systems are using for this function

  • System 1  It counts week on the bases of 1st January if week contains 1st January then this week numbered as week 1
  • System 2  It counts week on the bases of Thursday if week contains Thursday then this week numbered as week 1 of the year. This system is known as the European week numbering system it is the methodology specified in ISO 8601.
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