Free Online Utility
Week Number Calculator (ISO 8601)
Find the official ISO week number for today or any specific date. Widely used in international supply chains, agile sprints, and corporate reporting.
Official ISO 8601 Week Number
Week --
Year Elapsed--%
Week Start (Monday)--
Week End (Sunday)--
Total Weeks in Year52 Weeks
How to Determine the ISO Week Number
- Enter any calendar date (defaults to today).
- Instantly view the ISO week number (1 to 53), the Monday week start date, and Sunday week end date.
- See total weeks in that calendar year and percentage of year elapsed.
Frequently Asked Questions
What is the ISO 8601 week standard?
Under ISO 8601, Week 1 of any year is defined as the week containing the first Thursday of the year, and weeks always begin on Monday.
Why do some years have 53 weeks?
Years starting on Thursday, or leap years starting on Wednesday, contain 53 ISO weeks instead of the usual 52.
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