How to Use the WEEKNUM Function in Excel (video in khmer)

Hello everyone! Today i will show you how to use WEEKNUM formula in Microsoft Excel step by step.

If you have date in your spreadsheet (example: 2026-05-30) and you want to know what week number of the year it is (1 to 52 or 53), the WEEKNUM formula help you very fast and easy!

📚 Related Tutorial: Want to get the day of the week number instead? Check out How to Use WEEKDAY Function in Excel!

🛠️ Formula Syntax & How It Works

The WEEKNUM formula has two parts:

=WEEKNUM(serial_number, [return_type])

• serial_number: The date cell you want to check (example: A2 or "2026-05-30").
• return_type (Optional): Choose which day your work week start:
  • 1 (or leave empty): Week start on Sunday (Sunday = 1, Saturday = 7).
  • 2: Week start on Monday (Monday = 1, Sunday = 7).
  • 11: Week start on Monday (same like option 2).

📊 Simple Examples

Example 1: Week start on Sunday (Default)

If cell A2 contain date 2026-05-30:

=WEEKNUM(A2)

• Result: 23 (May 30, 2026 is in week 23 when week start on Sunday)

Example 2: Week start on Monday

If cell A2 contain date 2026-05-30:

=WEEKNUM(A2, 2)

• Result: 22 (May 30, 2026 is in week 22 when week start on Monday)

Example 3: Get Week Number for Today Date

If you want to know current week number for today:

=WEEKNUM(TODAY(), 2)

• Result: Show current week number automatically!

💡 Pro Tips for WEEKNUM Formula

1. Format Result Cell: After enter WEEKNUM formula, change cell format to General or Number so week number show clean without date formatting.
2. Choose Correct Return Type: Check your company office calendar if your work week start on Sunday (use 1) or Monday (use 2).
3. ISO Week Number Standard: If your office follow ISO standard (where week 1 is first week of year with at least 4 days), use return_type=21 or use =ISOWEEKNUM(A2).
4. Combine with IF Function: You can combine WEEKNUM with IF formula to group sales data by week automatically!

📚 Related Tutorials

• How to Use WEEKDAY Function in Excel
• How to Use DAY, MONTH, and YEAR in Excel
• How to Use NOW() and TODAY() in Excel
• How to Calculate Days Between Two Dates in Excel
• Top 15 Basic Excel Formulas for Beginners