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Formula generator for ISOWEEKNUM function

The ISOWEEKNUM function returns the number of the ISO week of the year where the provided date falls. ISO week numbering follows the ISO 8601 standard, where each week starts on a Monday and the first week of the year is the week that contains the first Thursday of the year.

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How to generate an ISOWEEKNUM formula using AI.

To obtain information on the ARRAY_CONSTRAIN formula, you could ask the AI chatbot the following question: “To get the ISOWEEKNUM formula, you can ask the AI chatbot something like: "Is there a formula in Excel that can return the ISO week number for a given date?"

ISOWEEKNUM formula syntax

The ISOWEEKNUM function in Excel is used to determine the ISO week number of a given date. The syntax for the function is: ISOWEEKNUM(date) Here, "date" refers to the specific date for which you want to find the ISO week number. The function returns a number between 1 and 53, representing the ISO week number of the given date. It's important to note that ISO week numbers follow the ISO 8601 standard, where the first week of the year is the week that contains at least 4 days of the new year. This means that the first week of the year may actually start in the previous year, and the last week of the year may extend into the next year. For example, the formula =ISOWEEKNUM("1/1/2022") would return 52, as the first week of 2022 starts on December 27, 2021, and ends on January 2, 2022. Overall, the ISOWEEKNUM function is a useful tool for working with week-based calculations in Excel, especially when dealing with international standards.

Use Cases & Examples

In these use cases, we use the ISOWEEKNUM function to determine the ISO week number for a given date. This function is particularly useful when working with international standards that define weeks starting on Monday and ending on Sunday.

Calculating ISO Week Number


Calculate the ISO week number for a given date.



Calculating Average Sales per Week


Calculate the average sales per week for a given range of dates.


AVERAGEIFS(sales, ISOWEEKNUM(date), week_number)

Counting Number of Orders in a Specific Week


Count the number of orders that fall within a specific ISO week.


COUNTIFS(orders, ISOWEEKNUM(date), week_number)

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