Please Note: This article is written for users of the following Microsoft Excel versions: 97, 2000, 2002, and 2003. If you are using a later version (Excel 2007 or later), this tip may not work for you. For a version of this tip written specifically for later versions of Excel, click here: Using the WEEKNUM Function.
Written by Allen Wyatt (last updated July 10, 2021)
This tip applies to Excel 97, 2000, 2002, and 2003
One of the functions provided in the Analysis ToolPak is WEEKNUM. This function is used, oddly enough, to return the week number represented by a particular date. You use the function in this way:
=WEEKNUM(A5,1)
In this instance, A5 contains a date serial number, and the value 1 indicates that WEEKNUM should assume that all weeks start on a Sunday. If you prefer your weeks to begin on Mondays, then you can use the value 2 instead.
You should realize that WEEKNUM always considers the first day of any given year to be in the first week of the year. Thus, it is possible for the above formula to return up to 54 weeks in a year. How can this be? Let's use the year 2011 as an example. In 2011 January 1 falls on a Saturday. As far as WEEKNUM is concerned, this is in the first week of the year. Now, January 2 for that year falls on a Sunday. Since WEEKNUM believes that every Sunday starts a new week, the second day of the week is considered in the second week of the year.
This is fine, until you get to the end of the year. The fifty-second week of 2011 ends (according to WEEKNUM) on December 24, and the fifty-third week begins on December 25 (a Sunday).
An even more interesting scenario is when the year begins on a Saturday and the year is a leap year. This happened in the year 2000. In that instance, the fifty-third week began on December 24, and the fifty-fourth week began on December 31.
ExcelTips is your source for cost-effective Microsoft Excel training. This tip (2326) applies to Microsoft Excel 97, 2000, 2002, and 2003. You can find a version of this tip for the ribbon interface of Excel (Excel 2007 and later) here: Using the WEEKNUM Function.
Dive Deep into Macros! Make Excel do things you thought were impossible, discover techniques you won't find anywhere else, and create powerful automated reports. Bill Jelen and Tracy Syrstad help you instantly visualize information to make it actionable. You’ll find step-by-step instructions, real-world case studies, and 50 workbooks packed with examples and solutions. Check out Microsoft Excel 2019 VBA and Macros today!
Got a tone of names from which you need to select a few random names? There are several ways you can extract what you ...
Discover MoreDoes your data require that you perform calculations using circular references? If so, then you'll want to be aware of ...
Discover MoreWhen working with dates and the relationship between dates, Excel provides a variety of worksheet functions that may ...
Discover MoreFREE SERVICE: Get tips like this every week in ExcelTips, a free productivity newsletter. Enter your address and click "Subscribe."
There are currently no comments for this tip. (Be the first to leave your comment—just use the simple form above!)
Got a version of Excel that uses the menu interface (Excel 97, Excel 2000, Excel 2002, or Excel 2003)? This site is for you! If you use a later version of Excel, visit our ExcelTips site focusing on the ribbon interface.
FREE SERVICE: Get tips like this every week in ExcelTips, a free productivity newsletter. Enter your address and click "Subscribe."
Copyright © 2026 Sharon Parq Associates, Inc.
Please Note:
This article is written for users of the following Microsoft Excel versions: 97, 2000, 2002, and 2003. If you are using a later version (Excel 2007 or later), this tip may not work for you. For a version of this tip written specifically for later versions of Excel, click here:
Comments