๐ Week Number Calculator
Enter a date to see the calculation
Enter a date and instantly find its ISO 8601 week number (which week of the year it falls in) along with its day-of-year count. Useful for weekly business reports or checking week-number notation in a schedule.
How to use
- Enter the date you want to check.
- The ISO week number and day-of-year count are shown automatically.
FAQ
What is an ISO week number?
A week number based on the ISO 8601 standard, where weeks start on Monday and week 1 is the week containing the year's first Thursday. Near year boundaries, the calendar year and the ISO week-numbering year can differ.
Does this support US-style (Sunday-start) week numbering?
No โ this tool only supports ISO 8601 (Monday-start) week numbering.
What is the day-of-year count?
The number of days that have elapsed since January 1st of that year, counting January 1st as day 1.