Week numbers 2026: calendar weeks with dates
Week numbers 2026: all 53 ISO calendar weeks of 2026 with their Monday and Sunday dates. 2026 is one of the rare years with 53 weeks, because 1 January 2026 falls on a Thursday.
With JavaScript on, this line names the week that contains today and marks it in the table.
Every week of 2026
ISO weeks run from Monday to Sunday. Week 1 of 2026 starts on Monday 29 December 2025 and week 53 ends on Sunday 3 January 2027. Dates outside 2026 show their year.
| Week | Monday | Sunday | Months |
|---|---|---|---|
| 1 | Mon 29 December 2025 | Sun 4 January | December and January |
| 2 | Mon 5 January | Sun 11 January | January |
| 3 | Mon 12 January | Sun 18 January | January |
| 4 | Mon 19 January | Sun 25 January | January |
| 5 | Mon 26 January | Sun 1 February | January and February |
| 6 | Mon 2 February | Sun 8 February | February |
| 7 | Mon 9 February | Sun 15 February | February |
| 8 | Mon 16 February | Sun 22 February | February |
| 9 | Mon 23 February | Sun 1 March | February and March |
| 10 | Mon 2 March | Sun 8 March | March |
| 11 | Mon 9 March | Sun 15 March | March |
| 12 | Mon 16 March | Sun 22 March | March |
| 13 | Mon 23 March | Sun 29 March | March |
| 14 | Mon 30 March | Sun 5 April | March and April |
| 15 | Mon 6 April | Sun 12 April | April |
| 16 | Mon 13 April | Sun 19 April | April |
| 17 | Mon 20 April | Sun 26 April | April |
| 18 | Mon 27 April | Sun 3 May | April and May |
| 19 | Mon 4 May | Sun 10 May | May |
| 20 | Mon 11 May | Sun 17 May | May |
| 21 | Mon 18 May | Sun 24 May | May |
| 22 | Mon 25 May | Sun 31 May | May |
| 23 | Mon 1 June | Sun 7 June | June |
| 24 | Mon 8 June | Sun 14 June | June |
| 25 | Mon 15 June | Sun 21 June | June |
| 26 | Mon 22 June | Sun 28 June | June |
| 27 | Mon 29 June | Sun 5 July | June and July |
| 28 | Mon 6 July | Sun 12 July | July |
| 29 | Mon 13 July | Sun 19 July | July |
| 30 | Mon 20 July | Sun 26 July | July |
| 31 | Mon 27 July | Sun 2 August | July and August |
| 32 | Mon 3 August | Sun 9 August | August |
| 33 | Mon 10 August | Sun 16 August | August |
| 34 | Mon 17 August | Sun 23 August | August |
| 35 | Mon 24 August | Sun 30 August | August |
| 36 | Mon 31 August | Sun 6 September | August and September |
| 37 | Mon 7 September | Sun 13 September | September |
| 38 | Mon 14 September | Sun 20 September | September |
| 39 | Mon 21 September | Sun 27 September | September |
| 40 | Mon 28 September | Sun 4 October | September and October |
| 41 | Mon 5 October | Sun 11 October | October |
| 42 | Mon 12 October | Sun 18 October | October |
| 43 | Mon 19 October | Sun 25 October | October |
| 44 | Mon 26 October | Sun 1 November | October and November |
| 45 | Mon 2 November | Sun 8 November | November |
| 46 | Mon 9 November | Sun 15 November | November |
| 47 | Mon 16 November | Sun 22 November | November |
| 48 | Mon 23 November | Sun 29 November | November |
| 49 | Mon 30 November | Sun 6 December | November and December |
| 50 | Mon 7 December | Sun 13 December | December |
| 51 | Mon 14 December | Sun 20 December | December |
| 52 | Mon 21 December | Sun 27 December | December |
| 53 | Mon 28 December | Sun 3 January 2027 | December and January |
Need the week for one date, or a date outside 2026? The week number calculator gives the ISO week, the US week and the day of the year for any date, and the dates of any week.
Why 2026 has 53 weeks
Most years have 52 numbered weeks. 2026 has 53 because of where 1 January lands. ISO 8601 makes week 1 the week that holds the first Thursday of the year, and in 2026 the first Thursday is 1 January itself. Week 1 therefore starts on Monday 29 December 2025 and ends on Sunday 4 January 2026, pulling the last three days of 2025 into the 2026 week-year. Fifty-two full weeks later there is still a Thursday left in December (31 December 2026), so it earns a week of its own: week 53, from 28 December to 3 January 2027. The first three days of 2027 belong to that week, not to 2027.
The last year with 53 weeks was 2020, and the next will be 2032. If you run anything weekly, 2026 has one more cycle than you might budget for: 53 payroll runs, 53 weekly reports, 53 sprint weeks.
ISO weeks and US (Sunday start) weeks in 2026
Printed wall calendars sold in the United States, and Excel's WEEKNUM function with its default setting, start weeks on Sunday and call the week with 1 January week 1. Because 1 January 2026 is a Thursday, their week 1 is 28 December 2025 to 3 January 2026, and Sunday 4 January is already week 2. From then on the Sunday-start number matches the ISO number from Monday to Saturday and runs one ahead on Sundays. The table below uses ISO numbers; the week number calculator shows both for any date.
Weeks that cross a month boundary
12 of the 53 weeks in 2026 straddle two months, so a week-based report line can land in either month depending on the rule you pick. Common choices are the month the Monday falls in, the month with the most days in the week, or the month the Thursday falls in (the ISO approach, which mirrors how weeks are assigned to years). Pick one and write it down: the weeks that cross are 1, 5, 9, 14, 18, 27, 31, 36, 40, 44, 49, 53.
See also week numbers for 2026 and 2027, or go straight to week numbers 2027. For deadlines in working days, the business days calculator skips weekends and your own holidays.
Questions people ask
How many weeks are in 2026?
2026 has 53 ISO weeks. 1 January 2026 is a Thursday, and any year that starts on a Thursday has 53 weeks under ISO 8601. Week 53 runs from 28 December to 3 January 2027.
What week is 1 January 2026?
1 January 2026 is in ISO week 1 of 2026, which starts on Monday 29 December 2025 and ends on Sunday 4 January 2026. Under the US (Sunday start) rule it is also week 1.
Which is the last week of 2026?
Week 53, from Monday 28 December 2026 to Sunday 3 January 2027. 31 December 2026 is a Thursday, so the week it sits in belongs to 2026 even though it runs three days into January 2027.
How many weeks in 2026 cross from one month into the next?
12 weeks: numbers 1, 5, 9, 14, 18, 27, 31, 36, 40, 44, 49, 53. Week 1 straddles December 2025 and January 2026, and week 53 straddles December 2026 and January 2027.