The WEEKNUM function accepts a date and returns the week number (1 through 54) of that date. The date must be in a valid format, so you have to use the DATE 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 the DATE function to 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 and the week containing the first Thursday of the year is numbered week 1. See ISOWEEKNUM for 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 the ISO day 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 to this spreadsheet for the examples of the WEEKNUM function shown above that you can study and use anywhere you would like.