Google Sheets ISOWEEKNUM Function

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


The Google Sheets ISOWEEKNUM returns the number of the ISO week of the year for a given date. ISO weeks begin on Monday and number 1 is the first week in that year.

The ISOWEEKNUM function can be used to get a week number from 1 to 54 that follows ISO standards in google sheets. The purpose of this function is to get ISO week number for a given data and its returned values is a number between 1 and 54.

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


The syntax of the ISOWEEKNUM function is as below:


Where the ISOWEEKNUM function arguments is:

  • Date -This is a required argument. The date for which to calculate the ISO week number. It must be a cell reference that containing a date value, number or a function that returning a date type in google sheets.


  • You can use the DATE function to enter into a date value, or it will be return errors for a text values.
  • If the date argument is not a valid date type, ISOWEEKNUM function returns the #VALUE! Error message.
  • You need to know the WEEKNUM function will also start week number 1 on the first day of the year, then increment week numbers on Sundays.

Google Sheets ISOWEEKNUM Function Examples

The below examples will show you how to use google sheets ISOWEEKNUM Function to get the ISO week number for a given date.

1# calculate the ISO week number for a given date in Cell B1, using the following formula:


google sheets isoweeknum function1

2# calculate the ISO WEEK number of current date

If you want to get the ISO week number for the current date in google sheets, and you can use the ISOWEEKNUM formula in combination with the TODAY function, just using the following formula:


google sheets isoweeknum function1 

3# calculate the ISO WEEK number with a date text string

You can enter a date text string into ISOWEEKNUM function instead of a cell reference that contain a date type value, just see the below formula:


google sheets isoweeknum function1