Week numbers follow ISO 8601: weeks start on Monday and week 1 is the week containing the year’s first Thursday. Some years have 53 weeks.
How to find a week number
- Today’s week is shown automatically.
- Pick another date to see its week.
- Scroll the table for all weeks of the year.
ISO vs US week numbers
ISO weeks (used in Europe, Pakistan and most business software) start on Monday. In the US some calendars start weeks on Sunday and count the week containing 1 January as week 1, so numbers can differ by one near the start of the year.
Frequently asked questions
Does every year have 52 weeks?
Most do; years that start on a Thursday (or leap years starting on a Wednesday) have 53 ISO weeks.
Updated October 2026 · Built and tested by Sharjeel Tahir · How our tools are tested