What week number is it?
Week 40
Monday 28 September to Sunday 4 October 2026
Week 40 of 53 in 2026. Today is Thursday 1 October 2026, day 274 of the year.
How week numbers work
The UK uses the ISO 8601 standard, as does most of Europe. Weeks run from Monday to Sunday. Week 1 is the week that contains the year's first Thursday, which is the same as the week that contains 4 January.
So the first few days of January can belong to the last week of the previous year. In 2027, Friday 1 to Sunday 3 January are still in week 53 of 2026, and week 1 of 2027 starts on Monday 4 January.
52 or 53 weeks?
A year has 52 weeks and one day, or two days in a leap year. Those spare days add up, so some years get a 53rd ISO week. This happens when a year starts on a Thursday, or when a leap year starts on a Wednesday. 2026 has 53 weeks. After that, the next 53-week years are 2032 and 2037. More on this on how many weeks are in a year.
Other week numbering systems
The US usually starts weeks on Sunday and counts the week containing 1 January as week 1. On some dates this gives a different number from ISO. In spreadsheets, =ISOWEEKNUM(A1) in Excel or Google Sheets gives the ISO week. Payroll, school and retail calendars may use their own week counts, so check which system someone means.
All weeks in 2026
| Week | Starts (Monday) | Ends (Sunday) |
|---|
See the weeks laid out month by month in the 2026 calendar, or work out a date a number of weeks ahead with weeks from today.
Frequently asked questions
How are week numbers worked out?
The UK and Europe use the ISO 8601 standard. Weeks run Monday to Sunday, and week 1 is the week that contains the first Thursday of the year, which is always the week containing 4 January.
Does every year have 52 weeks?
No. Most years have 52 ISO weeks, but a year that starts on a Thursday, or a leap year that starts on a Wednesday, has 53. 2026 has 53 weeks; the next 53-week years are 2032 and 2037.
How do I get the week number in Excel?
Use =ISOWEEKNUM(A1) for the ISO week number of the date in cell A1. The older WEEKNUM function uses a different rule unless you pass 21 as the second argument.