ISO 8601
Week number calculator
Look up the ISO week for any date — useful for reports, sprints, and school calendars.
Combine with the weekday calculator or a country calendar when aligning teams across regions.
ISO week lookup
ISO week
—
Week number FAQ
What is an ISO week number?
ISO 8601 weeks start on Monday. Week 1 is the week with the year’s first Thursday.
Can I find dates for a week number?
Yes. Enter a date to see its ISO week and the Monday–Sunday range for that week.