Skip to content

How to Use Excel ISOWEEKNUM Function?

Listen to this article.

ISOWEEKNUM Function in Excel: Microsoft Excel is a powerful data visualization and analysis program used all around the world. It uses spreadsheets to store, organize, or perform operations with formulas and functions. This application is developed for WindowsMacAndroid, and iOS. The major purpose of the software is to do complicated calculations which are difficult to do manually.

This article explains the usage of ISOWEEKNUM Function in Excel. Further, we have described the usage of this function with practical examples. Get the official version of MS Excel from the following link:

Excel ISOWEEKNUM FunctionPin
Excel ISOWEEKNUM Function

Description of ISOWEEKNUM Function

  • It is one of the built-in functions in Microsoft Excel.
  • The ISOWEEKNUM Function in Excel is used to find out the ISO week number of the year from the given date.
  • This Excel function will return a number between 1 to 52, specifying in which week the given date falls.


  • Here, you will see the syntax of the ISOWEEKNUM function.
  • To apply this function on your spreadsheet, you have to select a cell and enter the formula in the following format.
  • Once you enter the formula, just click on the Enter button to get the result.


Argument Explanation

  • Date: The date from which you want to get the ISO week number.

1) MS Excel stores the dates as sequential numbers and so it can be utilized in calculations. By default, January 1, 1900 – serial number 1 & January 1, 2008 – serial number 39448 (because it is 39,448 days after Jan 1, 1900).
2) #NUM! error – if the date argument is not a valid number, then the function returns this error.
3) #VALUE! error – if the date argument is not a valid date type, then the function returns this error.


Let’s look at some practical examples of the ISOWEEKNUM Function and explore how to use it in the Excel spreadsheet.

  • Initially, you have to open your Excel workbook on your PC and launch the worksheet that has data.
  • For instance, we have entered the sample dates in Column B and we will get the ISO week number of the given dates using the ISOWEEKNUM function.
Input ValuesPin
Input Values
  • Then, you have to enter the formula in the cell as shown below to get the result.
Enter the formulaPin
Enter the formula
  • After entering the formula, you need to click the Enter button to get the output, as shown below. You can drag down the cell to fill the remaining cells.

Input that Causes Error

  • If the date argument is not a valid number, then the function returns #NUM! error.
  • In case, the date argument is not a valid date type, then the function returns #VALUE! error.
Value ErrorPin
Value Error


We hope that this tutorial helped you to know the usage of the ISOWEEKNUM Function in Excel with detailed practical examples. If you have any queries/doubts, kindly share them in the below comment section. To learn more about Excel functions, then visit our webpage

Video Tutorial

The following video will show you how to apply the ISOWEEKNUM function in the Excel spreadsheet.

Related Articles


Leave a Reply

Your email address will not be published. Required fields are marked *

Share to...