When using WEEKNUM, the most common questions involve errors, unexpected results, and batch fill workflows; this FAQ includes 3 common questions and a short glossary.
FAQ
What should I do if WEEKNUM returns an error?
- Check whether the date argument is a valid date, a date reference, or a recognized serial value.
- Check whether the parentheses, commas, and number of arguments are complete.
- If the cell contains a text-form date, convert it to a standard date format and calculate again.
Why is the WEEKNUM result different from the week number I expected?
- Check whether the
return_typeargument is set. - Confirm whether your worksheet uses Sunday or Monday as the start of the week.
- If you need consistent reporting, use the same argument rule across the whole worksheet before summarizing data.
How can I use WEEKNUM in multiple cells at once?
- Enter the correct WEEKNUM formula in the first target cell.
- Drag the fill handle from the lower-right corner of the cell, or copy and paste the formula into the target range.
- Check whether relative references behave as expected, and use absolute references when needed.
Glossary
| Term | Definition |
|---|---|
| serial_number | The required WEEKNUM argument that represents the date value used for week-number calculation. |
| return_type | The optional WEEKNUM argument that defines which day a week starts on. |
| week number | The numbered week of a date within a year, often used in reporting, scheduling, and analysis. |