What week of the year is it? ISO and US week numbers
ISO 8601 (used in Europe, Australia, most of Asia, Excel's ISOWEEKNUM and many business systems): weeks start on Monday, and week 1 is the week that contains the first Thursday of the year. Early January days can belong to the last week of the previous year, and late December days to week 1 of the next.
US system (Outlook, most printed US calendars, Excel's WEEKNUM): weeks start on Sunday, and week 1 is the week that contains January 1, even if it has only one day in the new year.
Week numbers for 2027
| ISO week | Monday | Sunday |
|---|---|---|
| 1 | January 4, 2027 | January 10, 2027 |
| 2 | January 11, 2027 | January 17, 2027 |
| 3 | January 18, 2027 | January 24, 2027 |
| 4 | January 25, 2027 | January 31, 2027 |
| 5 | February 1, 2027 | February 7, 2027 |
| 6 | February 8, 2027 | February 14, 2027 |
| 7 | February 15, 2027 | February 21, 2027 |
| 8 | February 22, 2027 | February 28, 2027 |
| 9 | March 1, 2027 | March 7, 2027 |
| 10 | March 8, 2027 | March 14, 2027 |
| 11 | March 15, 2027 | March 21, 2027 |
| 12 | March 22, 2027 | March 28, 2027 |
| 13 | March 29, 2027 | April 4, 2027 |
| 14 | April 5, 2027 | April 11, 2027 |
| 15 | April 12, 2027 | April 18, 2027 |
| 16 | April 19, 2027 | April 25, 2027 |
| 17 | April 26, 2027 | May 2, 2027 |
| 18 | May 3, 2027 | May 9, 2027 |
| 19 | May 10, 2027 | May 16, 2027 |
| 20 | May 17, 2027 | May 23, 2027 |
| 21 | May 24, 2027 | May 30, 2027 |
| 22 | May 31, 2027 | June 6, 2027 |
| 23 | June 7, 2027 | June 13, 2027 |
| 24 | June 14, 2027 | June 20, 2027 |
| 25 | June 21, 2027 | June 27, 2027 |
| 26 | June 28, 2027 | July 4, 2027 |
| 27 | July 5, 2027 | July 11, 2027 |
| 28 | July 12, 2027 | July 18, 2027 |
| 29 | July 19, 2027 | July 25, 2027 |
| 30 | July 26, 2027 | August 1, 2027 |
| 31 | August 2, 2027 | August 8, 2027 |
| 32 | August 9, 2027 | August 15, 2027 |
| 33 | August 16, 2027 | August 22, 2027 |
| 34 | August 23, 2027 | August 29, 2027 |
| 35 | August 30, 2027 | September 5, 2027 |
| 36 | September 6, 2027 | September 12, 2027 |
| 37 | September 13, 2027 | September 19, 2027 |
| 38 | September 20, 2027 | September 26, 2027 |
| 39 | September 27, 2027 | October 3, 2027 |
| 40 | October 4, 2027 | October 10, 2027 |
| 41 | October 11, 2027 | October 17, 2027 |
| 42 | October 18, 2027 | October 24, 2027 |
| 43 | October 25, 2027 | October 31, 2027 |
| 44 | November 1, 2027 | November 7, 2027 |
| 45 | November 8, 2027 | November 14, 2027 |
| 46 | November 15, 2027 | November 21, 2027 |
| 47 | November 22, 2027 | November 28, 2027 |
| 48 | November 29, 2027 | December 5, 2027 |
| 49 | December 6, 2027 | December 12, 2027 |
| 50 | December 13, 2027 | December 19, 2027 |
| 51 | December 20, 2027 | December 26, 2027 |
| 52 | December 27, 2027 | January 2, 2028 |
Frequently asked questions
What week of the year is it?
The box at the top of this page shows today's week number, worked out live from your device's date. When this page was last built (Wednesday, November 11, 2026), it was ISO week 46 of 2026.
What week is it in the US?
Most US calendars and Outlook count weeks from Sunday, with week 1 being the week that contains January 1. That can be one higher than the ISO week number used in Europe, Australia and most business software. The box above shows both.
How many weeks are in a year?
A year has 52 weeks and 1 day (52 weeks and 2 days in a leap year), so most years have 52 ISO weeks and some have 53. 2027 has 52 ISO weeks.
How do I get the week number in Excel?
Use =ISOWEEKNUM(A1) for the ISO week number, or =WEEKNUM(A1) for the US system with weeks starting on Sunday. In Google Sheets the same functions work.
See also: how many days are left in the year and the date calculator.