Week Number Calculator
Find the ISO week number and week-year for any calendar date. ISO weeks start on Monday and week 01 is the week with the year’s first Thursday.
Week Number Calculator
Get the ISO week number and ISO year for any date. Essential for sprint planning and reporting.
- Shows ISO week, which starts on Monday and counts weeks with the year’s first Thursday.
- Useful for “which week of the year” and “current ISO week” queries.
- Combine with Day Number for deeper calendar reporting.
Why does the ISO year differ sometimes?
ISO weeks can belong to the previous or next year if they span the new year boundary.
Does it work worldwide?
Yes—ISO 8601 is an international standard and this calculator follows it.