Getting the Week Number From a Date in Excel

New WEEKNUM Function - ISO 8601 standard

Excel has had a week number function for many versions, but Excel 2013 added a new week number function that complies with the ISO 8601 standard week number.

The existing week number function is WEEKNUM and can be used as below, assuming cell A1 has a date
=WEEKNUM(A1)
The default week numbering starts on a Sunday, but there is an option to start the week on a Monday as follows
=WEEKNUM(A1,2)
The new function is ISOWEEKNUM and can be used as below
=ISOWEEKNUM(A1)
The ISO standard week begins on the week with the year’s first Thursday.

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2 thoughts on “Getting the Week Number From a Date in Excel

  1. Hi
    The calendar we use does not appear to be supported. Our week 1 for 2019 starts on Sunday 30/12/2018. It then runs in standard 5,4,4 weeks per month fashion.
    What formula should I use to return the week number from the date please.
    Many thanks
    Paul

    • Hi Paul
      If cell A1 has 30/12/18 or a date in 2019 in it then the following formula seems to work
      =WEEKNUM(A1+7,1)-1
      It should handle the other weeks as well.
      The 5,4,4 is a month issue rather than a week issue.
      Regards
      Naale