totn Excel Functions

MS Excel: How to use the ISOWEEKNUM Function (WS)

This Excel tutorial explains how to use the Excel ISOWEEKNUM function with syntax and examples.

Description

The Microsoft Excel ISOWEEKNUM function returns the ISO week number from a date value.

The ISOWEEKNUM function is a built-in function in Excel that is categorized as a Date/Time Function. It can be used as a worksheet function (WS) in Excel. As a worksheet function, the ISOWEEKNUM function can be entered as part of a formula in a cell of a worksheet.

Excel ISOWEEKNUM Function

If you want to follow along with this tutorial, download the example spreadsheet.

Download Example

Syntax

The syntax for the ISOWEEKNUM function in Microsoft Excel is:

ISOWEEKNUM( serial_date )

Parameters or Arguments

serial_date
The serial date value from which to calculate the week number. A serial date is how Excel stores dates internally and it represents the number of days since January 1, 1900.

Returns

The ISOWEEKNUM function returns a numeric value.

Note

  • See also the WEEKNUM function if you want specify what day is the first day of the week for the year.

Applies To

  • Excel for Office 365, Excel 2019, Excel 2016, Excel 2013

Type of Function

  • Worksheet function (WS)

Example (as Worksheet Function)

Let's look at some Excel ISOWEEKNUM function examples and explore how to use the ISOWEEKNUM function as a worksheet function in Microsoft Excel:

Excel ISOWEEKNUM Function

Column A displays the serial date parameter for the ISOWEEKNUM function formatted using mmm d, yyyy. Most often you will want a formatted date rather than a serial date.

Column B shows the date from column A as an unformatted serial date.

Based on the Excel spreadsheet above, the following ISOWEEKNUM examples would return:

=ISOWEEKNUM(A2)
Result: 1

=ISOWEEKNUM(A3)
Result: 7

=ISOWEEKNUM(A4)
Result: 13

=ISOWEEKNUM(A5)
Result: 52

=ISOWEEKNUM("3/19/2016")
Result: 11