Week Numbers 2027
2027 has 52 weeks. ISO week 1 runs from Monday 4 January to Sunday 10 January, and week 52 ends on Sunday, 2 January 2028. Weeks start on Monday (ISO 8601, used in the UK, Europe and most of the world). The last column gives the US-style week (Sunday start) for the same Monday.
All 2027 week numbers
| Week | Monday | Sunday | US week |
|---|---|---|---|
| 1 | 4 Jan | 10 Jan | 2 |
| 2 | 11 Jan | 17 Jan | 3 |
| 3 | 18 Jan | 24 Jan | 4 |
| 4 | 25 Jan | 31 Jan | 5 |
| 5 | 1 Feb | 7 Feb | 6 |
| 6 | 8 Feb | 14 Feb | 7 |
| 7 | 15 Feb | 21 Feb | 8 |
| 8 | 22 Feb | 28 Feb | 9 |
| 9 | 1 Mar | 7 Mar | 10 |
| 10 | 8 Mar | 14 Mar | 11 |
| 11 | 15 Mar | 21 Mar | 12 |
| 12 | 22 Mar | 28 Mar | 13 |
| 13 | 29 Mar | 4 Apr | 14 |
| 14 | 5 Apr | 11 Apr | 15 |
| 15 | 12 Apr | 18 Apr | 16 |
| 16 | 19 Apr | 25 Apr | 17 |
| 17 | 26 Apr | 2 May | 18 |
| 18 | 3 May | 9 May | 19 |
| 19 | 10 May | 16 May | 20 |
| 20 | 17 May | 23 May | 21 |
| 21 | 24 May | 30 May | 22 |
| 22 | 31 May | 6 Jun | 23 |
| 23 | 7 Jun | 13 Jun | 24 |
| 24 | 14 Jun | 20 Jun | 25 |
| 25 | 21 Jun | 27 Jun | 26 |
| 26 | 28 Jun | 4 Jul | 27 |
| 27 | 5 Jul | 11 Jul | 28 |
| 28 | 12 Jul | 18 Jul | 29 |
| 29 | 19 Jul | 25 Jul | 30 |
| 30 | 26 Jul | 1 Aug | 31 |
| 31 | 2 Aug | 8 Aug | 32 |
| 32 | 9 Aug | 15 Aug | 33 |
| 33 | 16 Aug | 22 Aug | 34 |
| 34 | 23 Aug | 29 Aug | 35 |
| 35 | 30 Aug | 5 Sept | 36 |
| 36 | 6 Sept | 12 Sept | 37 |
| 37 | 13 Sept | 19 Sept | 38 |
| 38 | 20 Sept | 26 Sept | 39 |
| 39 | 27 Sept | 3 Oct | 40 |
| 40 | 4 Oct | 10 Oct | 41 |
| 41 | 11 Oct | 17 Oct | 42 |
| 42 | 18 Oct | 24 Oct | 43 |
| 43 | 25 Oct | 31 Oct | 44 |
| 44 | 1 Nov | 7 Nov | 45 |
| 45 | 8 Nov | 14 Nov | 46 |
| 46 | 15 Nov | 21 Nov | 47 |
| 47 | 22 Nov | 28 Nov | 48 |
| 48 | 29 Nov | 5 Dec | 49 |
| 49 | 6 Dec | 12 Dec | 50 |
| 50 | 13 Dec | 19 Dec | 51 |
| 51 | 20 Dec | 26 Dec | 52 |
| 52 | 27 Dec | 2 Jan 2028 | 53 |
Weeks in each month of 2027
ISO weeks are not tied to months, so a week can start in one month and end in the next. The table gives the week number of the first and last day of each month.
| Month | Week of the 1st | Week of the last day |
|---|---|---|
| January | 53 (of 2026) | 4 |
| February | 5 | 8 |
| March | 9 | 13 |
| April | 13 | 17 |
| May | 17 | 22 |
| June | 22 | 26 |
| July | 26 | 30 |
| August | 30 | 35 |
| September | 35 | 39 |
| October | 39 | 43 |
| November | 44 | 48 |
| December | 48 | 52 |
Week numbers of key 2027 dates
| Date | Day | ISO week | US week |
|---|---|---|---|
| Friday 1 Jan | New Year's Day | 53 | 1 |
| Sunday 14 Feb | Valentine's Day | 6 | 8 |
| Friday 26 Mar | Good Friday | 12 | 13 |
| Sunday 28 Mar | Easter Sunday | 12 | 14 |
| Monday 3 May | UK Early May bank holiday | 18 | 19 |
| Monday 31 May | Memorial Day (US) | 22 | 23 |
| Monday 5 Jul | Independence Day (US, observed) | 27 | 28 |
| Monday 30 Aug | UK Summer bank holiday (England and Wales) | 35 | 36 |
| Sunday 31 Oct | Halloween | 43 | 45 |
| Thursday 25 Nov | Thanksgiving (US) | 47 | 48 |
| Saturday 25 Dec | Christmas Day | 51 | 52 |
| Friday 31 Dec | New Year's Eve | 52 | 53 |
How ISO week numbers work
ISO 8601 has three rules. Weeks start on Monday. Week 1 is the week that contains the first Thursday of the year, which is the same as the week that contains 4 January. A year has 52 weeks, or 53 when it starts on a Thursday (or on a Wednesday in a leap year). 2027 starts on a Friday, so it has 52. 2026 started on a Thursday, so it has 53 weeks, and its week 53 runs from Monday, 28 December 2026 to Sunday, 3 January 2027.
The US-style system (Sunday to Saturday, week 1 is the week with 1 January) gives 2027 a short week 1 of only 2 days in January, and 53 numbered weeks in total. Check which system your company or school uses before booking by week number.
See the weeks on a calendar: the 2027 calendar and each monthly page (for example January 2027) show the ISO week next to every row. To count working days between two weeks, use the working days calculator.
Questions
How many weeks are there in 2027?
2027 has 52 ISO weeks. Week 1 starts on Monday, 4 January 2027 and week 52 ends on Sunday, 2 January 2028. There is no week 53 in 2027: the next year with 53 ISO weeks is 2032.
When does week 1 of 2027 start?
ISO week 1 of 2027 runs from Monday 4 January to Sunday, 10 January 2027, because it is the first week that contains a Thursday of 2027 (7 January). 1 to 3 January 2027 still belong to week 53 of 2026.
What week number is Christmas 2027?
Christmas Day, Saturday, 25 December 2027, is in ISO week 51. On a US-style calendar, where weeks start on Sunday, it is week 52.
Why does my calendar show a different week number?
Europe and most of the world use ISO 8601 weeks (Monday start, week 1 contains the first Thursday). Many US calendars and Outlook by default count from the week that contains 1 January, starting on Sunday. In 2027, from Monday 4 January, the US-style number is one higher than the ISO number from Monday to Saturday and two higher on Sundays, because a US week starts on the Sunday that ends an ISO week. 1 to 3 January belong to ISO week 53 of 2026, and the US count reaches week 53.
How do I get the ISO week number in Excel or Google Sheets?
Use =ISOWEEKNUM(A1), where A1 holds the date. =WEEKNUM(A1) gives the US-style number (Sunday start); =WEEKNUM(A1,21) gives the ISO number in Excel.
Which week of 2027 is it today?
The box at the top of this page shows today's ISO week and highlights it in the table. It uses the date on your device.
Week rules: ISO 8601 (International Organization for Standardization). Every number on this page is calculated from the calendar, not typed by hand.