How to use
- The current week number is shown at the top.
- Pick any date to see its week number – or enter a week and year to get the date range.
- Below you'll find every week of the year from Monday to Sunday.
How are week numbers counted?
This tool uses the international standard ISO 8601, used in most of Europe and in business: weeks start on Monday, and week 1 is the week containing the year's first Thursday.
That's why January 1 can still belong to week 52 or 53 of the previous year. A year has 52 or 53 ISO weeks. In the US, weeks are often counted from Sunday with week 1 containing January 1, so numbers can differ by one.
Frequently asked questions
What week is it today?
The current week number is displayed at the top and updates automatically.
Why do some years have 53 weeks?
If a year starts on a Thursday (or on a Wednesday in leap years), it has 53 ISO weeks.
Why does my US calendar show a different number?
US calendars often start weeks on Sunday and count the week of January 1 as week 1. This tool follows ISO 8601.