How do I use WEEKNUM in Excel?
Use WEEKNUM when you want to return the week number. Enter Date cell, Return type in that order, then add optional arguments when needed.
Excel Function
WEEKNUM
Returns week number in a year.
WEEKNUM(serial_number, [return_type])Arguments
serial_number
RequiredEnter a date/reference-related value.
return_type
OptionalSets week-start system: 1/omitted = Sunday, 2 = Monday, 11-17 = Monday-to-Sunday starts, 21 = ISO week numbering.
Practice Preview
Use WEEKNUM to return the result with these settings (Date cell: B2 (cell B2 (Start Date in column B)), Return type: 2 (Monday = 1)).
Example Table
| # | ATask ID | BStart Date | CEnd Date | DNotes | EHoliday |
|---|---|---|---|---|---|
| 2 | T001 | 2026/03/01 | 2026/03/05 | Standard task | 2026/03/03 |
| 3 | T002 | 2026/03/03 | 2026/03/10 | Priority task | 2026/03/06 |
| 4 | T003 | 2026/03/05 | 2026/03/12 | Standard task | 2026/03/10 |
| 5 | T004 | 2026/03/08 | 2026/03/14 | Urgent task | 2026/03/12 |
| 6 | |||||
| 7 | |||||
| 8 |
How to Use (Formula)
=WEEKNUM(B2, 2)Result
10
Practice This Function
WEEKNUM FAQ
Where can I practice WEEKNUM?
Use the "Start Function Practice" button to jump straight into WEEKNUM drills.
What arguments does WEEKNUM use?
The main arguments are Date cell, Return type. Start with the required ones, then add optional arguments if needed.