Week number today: what week is it?

What week is it?

The top of the tool shows the current week, updated every day: its number, its dates from Monday to Sunday, whether it is odd or even, and today’s day of the year. Three tabs go further:

• Week of a date: pick any date to get its week number, the dates of that week and the public holidays it contains;
• Dates of a week: enter a week number and a year, such as week 12 of 2027, to see when it starts and ends;
• All weeks: the full list for a calendar year or an academic year (September to August), with each Monday, each Sunday and the public holidays.

Choose the holidays that apply to you: United States, United Kingdom (England and Wales) or India. It’s free, there’s nothing to sign up for, and everything runs in your browser.

How week numbers are counted

The tool follows ISO 8601, the international standard used across Europe and in most business planning:

• weeks start on Monday and end on Sunday;
• week 1 is the week that contains the year’s first Thursday, which is also the week that contains January 4;
• a week belongs to the year of its Thursday.

The first and last days of a year can therefore fall in a week of the neighboring year. Friday, January 1, 2027 is in week 53 of 2026, and week 1 of 2027 starts on Monday, January 4. Monday, December 30, 2024 was already in week 1 of 2025.

Many US calendars count differently: weeks start on Sunday and week 1 is simply the week that contains January 1. Depending on the year and the day of the week, their numbers can differ from the ISO number, usually by one. Check which system your company or school uses.

Years with 52 or 53 weeks

A year has 52 weeks plus one or two days. Those extra days add up, and some years have 53 ISO weeks: years that start on a Thursday, and leap years that start on a Wednesday. That was the case in 2015 and 2020, it is the case in 2026, and it will be again in 2032 and 2037. 2027 and 2028 have 52 weeks.

Week 53 of 2026 runs from Monday, December 28, 2026 to Sunday, January 3, 2027. Any schedule that assumes 52 weeks a year shifts by one week when 2027 begins.

Odd and even weeks

Many schedules alternate between odd and even weeks: shared custody, bin collection every other week, shift rotas or on-call duty. The tool shows whether each week is odd or even.

Watch out for years with 53 weeks: week 53 and the week 1 that follows are both odd. At the end of 2026, week 53 (December 28 to January 3) is followed by week 1 of 2027 (January 4 to 10), so an “every other week” schedule no longer matches odd and even numbers. If an agreement refers to odd and even weeks, check how it handles this case.

Week numbers for 2027, month by month

The weeks that touch each month of 2027 (a week that spans two months appears in both):

For the exact dates of every week, open the “All weeks” tab and choose 2027, or the 2026-2027 academic year, which starts in week 36.

Week numbers in Excel, Google Sheets and Outlook

• Excel and Google Sheets: =ISOWEEKNUM(A1) returns the ISO week number of the date in A1. =WEEKNUM(A1) on its own uses the US system (weeks starting on Sunday, week 1 containing January 1); =WEEKNUM(A1,21) returns the ISO number.
• Outlook: go to File, Options, Calendar, and tick “Show week numbers” in the display options.
• Google Calendar: in the settings, under view options, tick “Show week numbers”.

More free tools

• the days between dates calculator counts the days, business days and weeks between two dates, adds days to a date and works out an age;
• Claire, your life coach, helps you set goals and plan them week by week.