Excel WeekNum and ISOWeekNum Functions

Excel WeekNum and ISOWeekNum Functions. In this video, we will learn about how to use WeekNum and ISOWeekNUm Excel Functions. These functions are designed to help you extract the number of a week from a given date. Using this week numbers you can organize your data more efficiently.

These numbers would help you manage your transactions data orders data sales data attendance information and much more in a very easy to navigate format.


Excel WeekNum function will provide you information about a week number by taking in two parameters, “Serial_number and a “Return_type”.

The serial number has to be a date and cannot be a text value in order to operate the function properly. If you pass in a text value a problem can occur and the results may not be accurate or may result in an error. You should pass the value for the serial number using a date function or you should provide a reference to a cell that has a proper date in it.


ISOweekNum is designed in a slightly different manner. Use the following link to check out the definition of ISO: http://bit.ly/2laUw65

ISO week now will provide you information about the week number using a slightly different approach i.e. If a week 1 starts from the middle of the week where half of the week is the last week of the last year and half of the week is the first week of the beginning year that week will be considered as the last week of the previous year.

Click on the following button to download the file used in the demo to practice along with us.

As demonstrated in the video, the first week of 2016 is actually a part of the last week of 2015 and that is the reason when using ISOweekNum we got output as 53. Use these functions wisely wherever necessary. In case of trouble or doubt, right in the comments section below.

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Excel Learning Series – TOC

  1. Excel 2016 – Basics – Find Sum, Average, Min and Max
  2. Excel 2016 Difference Between Formulas and Functions
  3. Excel 2016 Copy Formulas or Functions
  4. Microsoft Excel Auto Fill
  5. Excel 2016 Manage Views using Freeze Panes
  6. Microsoft Excel – Saving Workbooks
  7. Excel Upper and Lower Text Functions
  8. Excel 2016 – Text Function – Proper
  9. Excel Text Functions – Trim Function
  10. Excel – Text Function Left Function
  11. Excel Text Function – Right Function
  12. Excel Text Functions – MID Function
  13. Excel Concatenate Text Function
  14. Excel Nested Functions
  15. Excel Search Function
  16. Excel – Calculate Age using Date Function Today
  17. Calculate Tenure in Excel with Days Function
  18. Autofill Dates in Excel
  19. Formatting Dates in Excel
  20. Excel Date Format Shortcut
  21. Calculating Sum of Time in Excel
  22. Calculate Expiry Date in Excel 2016 – EDATE
  23. Find Age or Tenure using DATEDIF in Excel 2016
  24. RandBetween – Generate Random Dates in Excel 2016
  25. Excel Weekday Function
  26. Excel WeekNum and ISOWeekNum Functions
  27. Excel Networkdays and Excel Networkdays.INTL
  28. Excel Workday and Workdays INTL Functions
  30. Calculate Time Difference in Excel
  31. Calculate Quarter in Excel
  32. Rounding Day, Hour and Minutes in Excel
  33. Excel Pay Rate and Downtime Cost Calculation
  34. Excel Logical Functions IF, AND, OR
  35. Calculate Bonus in Excel Using IF Function
  36. Excel Learning – SumIF and SumIFS
  37. How to use Excel Count Functions
  38. How to use VLOOKUP in Excel
  39. How to vLookup in a different workbook in Excel
  40. VLookup for Multiple Sheets with Example
  41. Excel Custom Quarters
  42. Vlookup Return Custom Value

We hope you find this article useful. In case you are stuck and or need help, feel free to drop a comment below or submit your question. Do share it further and add your feedback about the article in the comments section.

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Syed Hussaini

I am a Support Specialist with 15+ Years of experience and exposure in Training, website development on WordPress, Joomla, and Google Sites, Customer Support, IT Operations, Team Management, Knowledge Management. My engagement in a corporate environment and freelance projects has taught me to be highly productive and independent.

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