What Is the Week Number Calculator?
This is a simple online tool to
- See the current week number, its date range, and how many weeks are left in this year
- Find which week a specific date falls or fell in
- See which dates correspond to a given week
The current week number updates every Monday at 00:00. You can see the current time on our online clock page.
How to Use This Tool
Find the current week number
- Click the Current Week Number tab if it's not already active.
- The left-hand box shows the number of the week, corresponding dates, and how many weeks are left in this year.
See which week a date falls in
- Switch to the Date to Week Number tab.
- Click in the Date box to set a date in the calendar.
- Click the button to see the week that corresponds to the selected date.
See the dates in a given week
- Switch to the Week Number to Date tab.
- Enter the week number (between 1 and 53) and year.
- Click the button to see the date range for the selected week.
What Is a Week Number?
A week number represents a specific week in the year, from week 1 to week 52 (or 53).
In the ISO 8601 calendar format, weeks start on Monday and end on Sunday, and the first week of the year is the week containing the first Thursday of the year.
Since a year has just over 52 weeks, some years include a 53rd week. This happens when January 1 falls on a Thursday in a regular year, or on a Wednesday or Thursday in a leap year.
ISO 8601 is widely used but not universal. Other calendar systems organize weeks and months differently and sometimes use a different system to calculate the first week of the year.