Excel WEEKNUM function

This post will guide you how to use Excel WEEKNUM function with syntax and examples in Microsoft excel.


The Excel WEEKNUM function returns the week number of a specific date, and the returned value is ranging from 1 to 53. And this function will start to count the week number from January 1 and the Sunday is the first day in one week by default.

The WEEKNUM function is a build-in function in Microsoft Excel and it is categorized as a DATE and TIME Function.

The WEEKNUM function is available in Excel 2016, Excel 2013, Excel 2010, Excel 2007, Excel 2003, Excel XP, Excel 2000, Excel 2011 for Mac.


The syntax of the WEEKNUM function is as below:

=WEEKNUM (serial_number,[return_type])

Where the WEEKNUM function arguments is:

  • Serial_number –This is a required argument. An Excel date that you want to get the week number. The dates should be typed by the DATE function to make sure it is a valid Excel date. For example, use DATE(2018,3,20) to pass into the WEEKNUM function and then it will return the week number.
  • return_type – This is an optional argument. A number that determines the first day of the week for the year, the default value is 1.
Return_type Week begins on System
1 or omitted Sunday 1
2 Monday 1
11 Monday 1
12 Tuesday 1
13 Wednesday 1
14 Thursday 1
15 Friday 1
16 Saturday 1
17 Sunday 1
21 Monday 2


  • If serial_number is out of range for the current date base value, a #NUM! Error is returned.
  • If return_type is out of the range specified in the table above, a #NUM! Error is returned.
  • A serial date is how the Microsoft Excel stores dates and it represents the number of days since 1900-01-01, so the January 1, 1900 date is serial number 1 by default.

Excel WEEKNUM Function Examples

The below examples will show you how to use Excel WEEKNUM Function to return the week number from an Excel date.

1# get number of the week from a date value 2018/03/20, enter the following formula in Cell B1.


excel weeknum examples1

Related Functions

  • Excel WEEKDAY function
    The Excel WEEKDAY function returns a integer value representing the day fo the week for a given Excel date and the value is range from 1 to 7.The syntax of the WEEKDAY function is as below:=WEEKDAY (serial_number,[return_type])…
  • Excel WORKDAY function
    The Excel WORKDAY function returns a serial number that represents a date that is the indicated number of working days before or after the starting date you specified.The syntax of the WORKDAY function is as below:=WORKDAY(start_date, days, [holidays])…
  • Excel DAY function
    The Excel DAY function returns a day of a date (from 1 to 31).The DAY function is a build-in function in Microsoft Excel and it is categorized as a DATE and TIME Function.The syntax of the DAY function is as below:= DAY (date_value)…
  • Excel EDATE function
    TThe Excel EDATE function returns the serial number that represents the date that is a specified number of months before or after a specified date.The syntax of the EDATE function is as below:=EDATE (start_date, months)…
  • Excel DATE function
    The Excel DATE function returns the serial number for a date.The syntax of the DATE function is as below:= DATE (year, month, day)…

More Excel WEEKNUM Function Examples

  • Converting Week Number to Date
    You need to create a formula based on the MAX function, the DATE function and the WEEKDAY function to convert week number to a date in Excel.…

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