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Excel WEEKNUM Function

You are here: Home / Excel Functions / Excel WEEKNUM Function

The Excel WEEKNUM function returns the week number (between 1 and 54) of a date serial number. e.g. 1st Jan 2017 is in week number 1 of the year.

There are two types of systems available with this function:

- System 1 where the week containing January 1 is the first week of the year, and is numbered week 1.

- System 2 starts with the first Thursday of the year being in week 1. This system is the methodology specified in ISO 8601, which is commonly known as the European week numbering system.

Excel WEEKNUM Function Syntax

Syntax: = WEEKNUM(serial_number, [return_type])
 

Where the serial_number is a date in a format Excel recognises known as the date-time serial number.

Note: The return type argument is optional, if omitted it will default to return type 1.

Below is a list of the return type options available:

Excel WEEKNUM Function

Tip: Return types 2 and 11 for Monday are the same as one another. Type 2 is only included for backward compatibility with earlier versions of Excel. Likewise, return type 1 for Sunday.

Excel WEEKNUM Function Examples

The table below contains some examples of WEEKNUM formulas using different return types.

Date   Return Type Return Type Day WEEKNUM Formula Result
Sun, Jan 01, 2017 1 Sunday 1
Sun, Jan 01, 2017 2 Monday 1
Sun, Jan 01, 2017 11 Monday 1
Sun, Jan 01, 2017 12 Tuesday 1
Sun, Jan 01, 2017 13 Wednesday 1
Sun, Jan 01, 2017 14 Thursday 1
Sun, Jan 01, 2017 15 Friday 1
Sun, Jan 01, 2017 16 Saturday 1
Sun, Jan 01, 2017 17 Sunday 1
Sun, Jan 01, 2017 21 Monday 52
Mon, Mar 13, 2017 1 Sunday 11
Mon, Mar 13, 2017 2 Monday 12
Mon, Mar 13, 2017 11 Monday 12
Mon, Mar 13, 2017 12 Tuesday 11
Mon, Mar 13, 2017 13 Wednesday 11
Mon, Mar 13, 2017 14 Thursday 11
Mon, Mar 13, 2017 15 Friday 11
Mon, Mar 13, 2017 16 Saturday 11
Mon, Mar 13, 2017 17 Sunday 11
Mon, Mar 13, 2017 21 Monday 11
Thu, Jan 05, 2017 1 Sunday 1
Thu, Jan 05, 2017 2 Monday 2
Thu, Jan 05, 2017 11 Monday 2
Thu, Jan 05, 2017 12 Tuesday 2
Thu, Jan 05, 2017 13 Wednesday 2
Thu, Jan 05, 2017 14 Thursday 2
Thu, Jan 05, 2017 15 Friday 1
Thu, Jan 05, 2017 16 Saturday 1
Thu, Jan 05, 2017 17 Sunday 1
Thu, Jan 05, 2017 21 Monday 1
 

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Related Tutorials

Excel MONTH Function Returns the month from a date serial number.
Excel DAY Function Returns the day (of the month) from a date serial number
Excel YEAR Function Returns the year from a date serial number
Excel End of Period Dates Calculate fiscal period end dates

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