What Week Is It? Current Week Number
The current week number is shown in large type, with its dates from Monday to Sunday. You can also find the week of any date, the dates of any week and the full list of weeks for a year.
- ISO 8601 standard
- Current week
- List of weeks
- Free, no sign-up
100% private — Everything is processed directly in your browser: your files, voice, and image are never sent to Chatzam's servers.
How to find a week number
-
Read the current week
The big number at the top is the current week number, based on your device's date, with its start and end dates.
-
Pick a date or a week
Enter a date to get its week number, or enter a week number and a year to get its dates.
-
Browse the year
The table lists every week of the chosen year with its dates; the current week is highlighted.
Everything about week numbers
Today's week, front and center
The number appears as soon as the page opens, along with the day of the week and the number of weeks in the year.
Works both ways
From a date to its week number, or from a week number to its dates from Monday to Sunday.
Every week of the year
52 or 53 weeks listed with their dates, for any year from 1 to 9999.
ISO or US
The ISO 8601 standard used in the UK and most of Europe is the default; one button switches to the US week numbering system.
The ISO 8601 standard: how weeks are numbered
In the UK and most European countries, weeks follow the ISO 8601 standard, which is also widely used in business and software. Each week starts on Monday and ends on Sunday. Week 1 is the week that contains the first Thursday of January, which means it always contains January 4. As a result, January 1, 2 and 3 can belong to the last week of the previous year, and December 29, 30 and 31 can belong to week 1 of the following year. For example, Friday, January 1, 2027 is in week 53 of 2026, and week 1 of 2027 starts on Monday, January 4. Conversely, Monday, December 30, 2024 was already in week 1 of 2025.
Why some years have 53 weeks
Fifty-two weeks make 364 days, one or two days short of a full year. Those extra days add up, so every so often an ISO year has a 53rd week. This happens when the year starts on a Thursday, or when a leap year starts on a Wednesday. 2020, a leap year that started on a Wednesday, had 53 weeks, and so does 2026, which starts on a Thursday. The next ones will be 2032, 2037 and 2043. Over a full 400-year calendar cycle, 71 years have 53 weeks and the rest have 52. This matters for schedules, weekly payroll and statistics: a 53-week year has one more week to plan for. The table shows the exact number of weeks for each year.
Week numbers in the United States
The United States doesn't use the ISO standard. US weeks start on Sunday, and week 1 is the week that contains January 1, even if it includes only one or two days of January. The numbers therefore often differ by one between the two systems, especially at the start of the year: Sunday, January 3, 2021 was in week 53 of 2020 under ISO rules, but in week 2 of 2021 under the US system. A US year can even have 54 weeks, like 2028, a leap year that starts on a Saturday. If you share a schedule with partners in Europe, or if a calendar app shows an unexpected number, switch to "United States" to compare the two systems.
Frequently Asked Questions
What week is it today?
The number shown in large type at the top of the page is the current week, according to the ISO standard used in the UK and Europe. It's calculated from your device's date and updates automatically. Choose "United States" to see the US week number.
How many weeks are there in a year?
52 or 53 under the ISO standard. 2026 has 53 weeks and 2027 has 52. The table of weeks shows the exact number for the chosen year.
When does week 1 start?
It's the Monday-to-Sunday week that contains the first Thursday of January. So it can start in late December: week 1 of 2026 started on Monday, December 29, 2025.
Why is January 1 sometimes in week 52 or 53?
When January 1 falls on a Friday, Saturday or Sunday, the week that contains it has more days from the previous year, so it stays the last week of that year.
Is the week number the same in every country?
No. The UK and most European countries follow the ISO 8601 standard, while the United States starts the week on Sunday and counts the week containing January 1 as week 1. The "United States" button shows that numbering.