Current Week Number

See the current week number and the dates included in this week. Week numbers on this page follow the international ISO 8601 week-numbering system.

CURRENT WEEK NUMBER

Week —

Loading current week…

ISO week year —
Weeks in year —
Weeks remaining —
Day of week —

ISO weeks start on Monday and end on Sunday.

What is the current week number?

The current week number is shown above together with the dates for Monday through Sunday.

ISO week numbers are commonly used in business, project planning, logistics, production schedules and calendars.

Each week is assigned a number from 1 to 52 or 53, depending on the year.

How do week numbers work?

This page uses the ISO 8601 week-numbering system.

Under this system:

  • A week starts on Monday.
  • A week ends on Sunday.
  • Week 1 is the week containing the first Thursday of the year.
  • Week 1 always contains January 4.
  • A year normally has 52 weeks, but some years have 53.

This means that the first few days of January can sometimes belong to the final numbered week of the previous ISO year.

Likewise, the final days of December can sometimes belong to week 1 of the following ISO year.

The ISO system defines Monday as the first day of the week and uses the first-Thursday rule to determine week 1.

When does the current week start and end?

Under ISO 8601, every numbered week runs from:

Monday through Sunday

For example:

  • Monday is the first day of the week.
  • Friday is the fifth day.
  • Saturday and Sunday form the weekend.
  • Sunday is the final day of the ISO week.

The current week tool above shows the exact Monday and Sunday dates for this week.

When is week 1?

ISO week 1 is the week containing January 4.

Another way to define it is:

Week 1 is the first week of the year containing a Thursday.

For example, if January 1 falls on Friday, Saturday or Sunday, those days can still belong to the final ISO week of the previous year.

The first Monday after that begins ISO week 1.

Why can January 1 belong to the previous year?

Calendar years and ISO week-numbering years do not always begin on the same day.

If January 1 falls late in the week, it can belong to week 52 or week 53 of the previous ISO year.

This is why a date can have:

  • Calendar year: 2027
  • ISO week year: 2026

for a few days around New Year.

The same thing can happen at the end of December, when some dates may already belong to week 1 of the next ISO year.

How many weeks are in a year?

Most years contain 52 ISO weeks.

Some years contain 53 weeks.

A normal calendar year contains 365 days, which is 52 weeks plus one day.

A leap year contains 366 days, which is 52 weeks plus two days.

Depending on how those extra days fall within the ISO week-numbering system, the year may receive a 53rd week.

Does every country use the same week numbers?

No.

ISO 8601 is widely used internationally, especially in Europe and in business environments, but calendar conventions differ between countries.

ISO calendars begin the week on Monday.

In countries such as the United States, calendars are often displayed with Sunday as the first day of the week, although different organizations may still use ISO week numbers for business and planning.

When sharing a week number internationally, it is therefore useful to specify that you mean an ISO week number.

Why are week numbers useful?

Week numbers provide a short way to refer to a seven-day period without writing the full date range.

For example, instead of saying:

“Monday August 24 through Sunday August 30”

you can simply say:

“Week 35”

This is useful for:

  • Project planning
  • Work schedules
  • Production planning
  • Logistics
  • Shipping
  • School calendars
  • Construction schedules
  • Release planning
  • Delivery forecasts
  • Reporting periods

How to find the week number for another date

If you need the week number for a date other than today, use the Week Number Calculator.

Enter any date and the calculator can show:

  • ISO week number
  • ISO week year
  • Monday of that week
  • Sunday of that week
  • Day of the week

You can also see week numbers throughout the year in our calendar.

Current week, today and calendar

These related tools can help with other date and calendar questions:

Frequently asked questions

What week number is it right now?

The current ISO week number is displayed at the top of this page and updates automatically as the weeks change.

When does the week number change?

Under ISO 8601, the week number changes at the beginning of Monday.

Does an ISO week start on Sunday?

No. ISO weeks start on Monday and end on Sunday.

What is the first week of the year?

Week 1 is the week containing January 4, which is also the first week containing a Thursday.

Can a year have 53 weeks?

Yes. Some ISO week-numbering years contain week 53.

Can January 1 be in week 52 or 53?

Yes. January 1 can belong to the final ISO week of the previous year.

Can December 31 be in week 1?

Yes. Some final days of December can belong to ISO week 1 of the following year.

Are week numbers the same everywhere?

No. Different countries and organizations can use different week conventions. This page uses ISO 8601 week numbers.

Where can I find the week number for another date?

Use the Week Number Calculator to enter any date and find its ISO week number.