What Week Is It?
The current ISO week number is shown below, calculated from your device's date. Weeks start on Monday, and week 1 is the week containing the year's first Thursday.
Last updated: 8 November 2026
Current ISO week number
Week number for any date
How week numbers work
Most of Europe and much of the business world use the ISO 8601 week system. Each week starts on Monday. Week 1 is the week that contains the first Thursday of the year — equivalently, the week that contains 4 January. As a result, a year has either 52 or 53 weeks, and the first days of January can belong to the last week of the previous year. For example, Friday 1 January 2027 is in week 53 of 2026, and week 1 of 2027 starts on Monday 4 January.
The United States often uses a different convention, where weeks start on Sunday and week 1 contains 1 January. If a colleague's week number is one off from yours, that is usually why.
Week numbers 2027
2027 has 52 ISO weeks. Week 1 runs from 4 to 10 January 2027 and week 52 from 27 December 2027 to 2 January 2028.
| Week | Monday – Sunday |
|---|---|
| Week 1 | Monday 4 January – Sunday 10 January 2027 |
| Week 2 | Monday 11 January – Sunday 17 January 2027 |
| Week 3 | Monday 18 January – Sunday 24 January 2027 |
| Week 4 | Monday 25 January – Sunday 31 January 2027 |
| Week 5 | Monday 1 February – Sunday 7 February 2027 |
| Week 6 | Monday 8 February – Sunday 14 February 2027 |
| Week 7 | Monday 15 February – Sunday 21 February 2027 |
| Week 8 | Monday 22 February – Sunday 28 February 2027 |
| Week 9 | Monday 1 March – Sunday 7 March 2027 |
| Week 10 | Monday 8 March – Sunday 14 March 2027 |
| Week 11 | Monday 15 March – Sunday 21 March 2027 |
| Week 12 | Monday 22 March – Sunday 28 March 2027 |
| Week 13 | Monday 29 March – Sunday 4 April 2027 |
| Week 14 | Monday 5 April – Sunday 11 April 2027 |
| Week 15 | Monday 12 April – Sunday 18 April 2027 |
| Week 16 | Monday 19 April – Sunday 25 April 2027 |
| Week 17 | Monday 26 April – Sunday 2 May 2027 |
| Week 18 | Monday 3 May – Sunday 9 May 2027 |
| Week 19 | Monday 10 May – Sunday 16 May 2027 |
| Week 20 | Monday 17 May – Sunday 23 May 2027 |
| Week 21 | Monday 24 May – Sunday 30 May 2027 |
| Week 22 | Monday 31 May – Sunday 6 June 2027 |
| Week 23 | Monday 7 June – Sunday 13 June 2027 |
| Week 24 | Monday 14 June – Sunday 20 June 2027 |
| Week 25 | Monday 21 June – Sunday 27 June 2027 |
| Week 26 | Monday 28 June – Sunday 4 July 2027 |
| Week 27 | Monday 5 July – Sunday 11 July 2027 |
| Week 28 | Monday 12 July – Sunday 18 July 2027 |
| Week 29 | Monday 19 July – Sunday 25 July 2027 |
| Week 30 | Monday 26 July – Sunday 1 August 2027 |
| Week 31 | Monday 2 August – Sunday 8 August 2027 |
| Week 32 | Monday 9 August – Sunday 15 August 2027 |
| Week 33 | Monday 16 August – Sunday 22 August 2027 |
| Week 34 | Monday 23 August – Sunday 29 August 2027 |
| Week 35 | Monday 30 August – Sunday 5 September 2027 |
| Week 36 | Monday 6 September – Sunday 12 September 2027 |
| Week 37 | Monday 13 September – Sunday 19 September 2027 |
| Week 38 | Monday 20 September – Sunday 26 September 2027 |
| Week 39 | Monday 27 September – Sunday 3 October 2027 |
| Week 40 | Monday 4 October – Sunday 10 October 2027 |
| Week 41 | Monday 11 October – Sunday 17 October 2027 |
| Week 42 | Monday 18 October – Sunday 24 October 2027 |
| Week 43 | Monday 25 October – Sunday 31 October 2027 |
| Week 44 | Monday 1 November – Sunday 7 November 2027 |
| Week 45 | Monday 8 November – Sunday 14 November 2027 |
| Week 46 | Monday 15 November – Sunday 21 November 2027 |
| Week 47 | Monday 22 November – Sunday 28 November 2027 |
| Week 48 | Monday 29 November – Sunday 5 December 2027 |
| Week 49 | Monday 6 December – Sunday 12 December 2027 |
| Week 50 | Monday 13 December – Sunday 19 December 2027 |
| Week 51 | Monday 20 December – Sunday 26 December 2027 |
| Week 52 | Monday 27 December – Sunday 2 January 2028 |
Frequently asked questions
- What week is it?
- The live display above shows the current ISO week number for your date.
- How many weeks are in 2027?
- 52 ISO weeks.
- Does 2026 have 53 weeks?
- Yes. 2026 has 53 ISO weeks; week 53 runs from 28 December 2026 to 3 January 2027.
- When does week 1 of 2027 start?
- Monday 4 January 2027.
Sources: ISO 8601 date and time format