Week Number Calculator
Check the ISO week number for any date, see the Monday to Sunday range for that week, and confirm how many ISO weeks remain in the year.
Choose a date to calculate the ISO week number.
Total ISO weeks this year: -
How to Use This Tool
- Select a date or click a quick example to load a common calendar edge case.
- Read the ISO week number and ISO year for the selected date.
- Use the Monday and Sunday boundaries as your reporting or sprint window.
What This Page Answers
- What ISO week number is this date?
- Which ISO year does this week belong to?
- When does this week start and end?
- How many ISO weeks are left this year?
Frequently Asked Questions
An ISO week number is the week index defined by ISO 8601, where weeks start on Monday and week 1 is the week containing the first Thursday of the year.
Dates near the start or end of a calendar year can belong to the previous or next ISO week year because ISO weeks are based on complete Monday to Sunday blocks.
Most ISO years have 52 weeks, but some have 53 depending on how the calendar days align around January 1 and December 31.
The calculator finds the Monday and Sunday that bound the selected ISO week, so you can see the exact reporting window for that week.