Google Sheets WEEKNUM Function

This post will guide you how to use Google Sheets WEEKNUM function with syntax and examples.


The Google Sheets 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 can be used to get a number representing the week of the year where the provided date falls in google sheets. The purpose of this function is to get the week number for a given date and it will return a number between 1 and 54.

The WEEKNUM function is a build-in function in Google Sheets and it is categorized as a Date function.


The syntax of the WEEKNUM function is as below:

=WEEKNUM (serial_number,[return_type])

Where the WEEKNUM function arguments is:

  • Serial_numberThis is a required argument. A 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 date. For example, use DATE(2021,3,20) to pass into the WEEKNUM function and then it will return the week number.
  • return_typeThis 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 google sheets 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.

Google Sheets WEEKNUM Function Examples

The below examples will show you how to use google sheets WEEKNUM Function to return the week number from a date.

1# get number of the week from a date value 2021/03/20, enter the following formula in Cell B1.


google sheet weeknum function1