The WEEKNUM function accepts a date and returns the week number (1 through 54) of that date. The date must be in avalid format, so you have to use theDATE function, wrap it in quotes, or use a cell reference to a cell containing a date.

If your days, months, and years are in different cells, use theDATE functionto combine them.



  • date- The date for which you want the week number. This is required.
  • [type]- Optional specification of which day is the first day of the week. And, which week is the first week of the year.
    • 1 (or not specified) - Week begins on Sunday
    • 2  - Week begins on Monday
    • 11 - Week begins on Monday (same as #2)
    • 12 - Week begins on Tuesday
    • 13 - Week begins on Wednesday
    • 14 - Week begins on Thursday
    • 15 - Week begins on Friday
    • 16 - Week begins on Saturday
    • 17 - Week begins on Sunday
    • 21 - Week begins on Monday andthe week containing the first Thursday of the year is numbered week 1. SeeISOWEEKNUMfor more.

Related functions

DATE- Takes separate year, month, and day values and returns them as a date

DATEVALUE- Returns the serial value of a date

ISOWEEKNUM- Returns theISOday of the week. Similar to WEEKNUM.


#NUM- The inputs are numbers but are not valid dates. This could happen if you used the 35th day of November.

#VALUE!- The inputs are something that doesn't convert to a number such as "The other day" or "Yester-yester-day".


 Live examples in Sheets 

Go tothis spreadsheetfor the examples of the WEEKNUM function shown above that you can study and use anywhere you would like.