Week number today: what week is it?

The current week number according to the ISO 8601 standard used in the UK and across Europe, with its parity (even or odd) and its Monday to Sunday dates. Updated automatically every day.

Today is Sunday 25 October 2026

It is currently

week 43

odd

Monday to Sunday: 19 – 25 October 2026

Day of the week

7 / 7

Last day of the week

Next week

W44 even

Starts Monday 26 October

Weeks in the year

In 2026 (ISO year)

Need to check another date, such as a handover day or a holiday? Our even or odd week checker gives the week number and parity of any day.

How are week numbers calculated?

In the UK and most of Europe, weeks are numbered according to the international standard ISO 8601. The rules are simple:

Weeks start on Monday and end on Sunday.
Week 1 is the week that contains 4 January. Put differently, it contains the first Thursday of the year, so at least 4 of its 7 days fall in January.
A year therefore has 52 or 53 weeks. It has 53 when it starts on a Thursday (or on a Wednesday in a leap year).
The first days of January can belong to the last week of the previous year, and the last days of December to week 1 of the next year.

For example, in 2026 week 1 started on Monday 29 December 2025 and the last week (week 53) ends on Sunday 3 January 2027. So 2026 has 53 weeks, which only happens every 5 or 6 years: read more about week 53.

What about the United States?

Week numbering is not the same everywhere. In the US and Canada, weeks usually start on Sunday and week 1 is the week containing 1 January. The number can then differ by one from the ISO week, especially at the start and end of the year. If you work with American colleagues or software set to US defaults, check which system is being used before you agree on a "week 12" deadline.

Even or odd week: why it matters

Week numbers are used for all kinds of schedules: shift rotations, bin collections, school timetables and, above all, shared custody. Many parenting plans say, for instance, that the children stay with one parent in even weeks and with the other in odd weeks. Parity switches every Monday.

Watch out when a 53-week year ends: week 53 (odd) is followed by week 1 (also odd). Two odd weeks in a row break the alternation unless your arrangement says what happens in that case.

All week numbers in 2026

Here are the 53 weeks of 2026 with their dates and parity (E = even, O = odd). The current week is outlined. For a printable version, see the 2026 even and odd week calendar.

Week	Dates	E/O
January 2026 Week 1–5
1	29 December – 4 January	O
2	5 – 11 January	E
3	12 – 18 January	O
4	19 – 25 January	E
5	26 January – 1 February	O
February 2026 Week 6–9
6	2 – 8 February	E
7	9 – 15 February	O
8	16 – 22 February	E
9	23 February – 1 March	O
March 2026 Week 10–13
10	2 – 8 March	E
11	9 – 15 March	O
12	16 – 22 March	E
13	23 – 29 March	O
April 2026 Week 14–18
14	30 March – 5 April	E
15	6 – 12 April	O
16	13 – 19 April	E
17	20 – 26 April	O
18	27 April – 3 May	E
May 2026 Week 19–22
19	4 – 10 May	O
20	11 – 17 May	E
21	18 – 24 May	O
22	25 – 31 May	E
June 2026 Week 23–26
23	1 – 7 June	O
24	8 – 14 June	E
25	15 – 21 June	O
26	22 – 28 June	E
July 2026 Week 27–31
27	29 June – 5 July	O
28	6 – 12 July	E
29	13 – 19 July	O
30	20 – 26 July	E
31	27 July – 2 August	O
August 2026 Week 32–35
32	3 – 9 August	E
33	10 – 16 August	O
34	17 – 23 August	E
35	24 – 30 August	O
September 2026 Week 36–39
36	31 August – 6 September	E
37	7 – 13 September	O
38	14 – 20 September	E
39	21 – 27 September	O
October 2026 Week 40–44
40	28 September – 4 October	E
41	5 – 11 October	O
42	12 – 18 October	E
43	19 – 25 October	O
44	26 October – 1 November	E
November 2026 Week 45–48
45	2 – 8 November	O
46	9 – 15 November	E
47	16 – 22 November	O
48	23 – 29 November	E
December 2026 Week 49–53
49	30 November – 6 December	O
50	7 – 13 December	E
51	14 – 20 December	O
52	21 – 27 December	E
53	28 December – 3 January	O

How to find the week number in your apps

Excel and Google Sheets

The formula =ISOWEEKNUM(A1) returns the ISO week number of the date in A1, in both Excel and Google Sheets; use =ISOWEEKNUM(TODAY()) for the current week. Avoid WEEKNUM without a second argument: by default it uses US numbering (weeks starting on Sunday). To get the parity, use =IF(ISEVEN(ISOWEEKNUM(A1)),"Even","Odd").

iPhone and iPad

In the Calendar app, week numbers are turned on in Settings, in the Calendar section (under "Apps" on recent versions of iOS), with the Week Numbers option. Even easier: our Even / Odd iPhone app shows the current week and its parity right on your home screen with its widget, without opening anything.

Google Calendar

On the web, open Settings, go to View options and tick Show week numbers. Set the start of the week to Monday as well, so it matches the ISO standard.

Outlook

In Outlook's calendar settings, turn on the option to show week numbers. In Outlook for Windows, also check the "first week of year" setting: choose First 4-day week and Monday as the first day of the week to get ISO numbering.

Frequently asked questions about week numbers

What week number is it today?

The current week is shown at the top of this page: its number, parity and Monday to Sunday dates are recalculated automatically on every visit, according to the ISO 8601 standard.

How many weeks are there in 2026?

2026 has 53 ISO weeks. Week 1 starts on Monday 29 December 2025 and week 53 ends on Sunday 3 January 2027.

When does week 1 start?

Week 1 is the week that contains 4 January, which is also the week of the first Thursday of the year. It can therefore start in late December of the previous year: in 2026, it started on Monday 29 December 2025.

Do weeks start on Monday or Sunday?

Under ISO 8601, used in the UK and Europe, weeks start on Monday. In the US, weeks usually start on Sunday and week 1 is the week containing 1 January, so the number can be off by one.

How do I know if a week is even or odd?

A week is even if its number can be divided by 2 (2, 4, 6…) and odd otherwise (1, 3, 5…). Parity changes every Monday. After a 53-week year, week 53 and the following week 1 are both odd.

How do I get the week number in Excel?

Use =ISOWEEKNUM(date) in Excel or Google Sheets. It returns the week number according to ISO 8601, unlike WEEKNUM, which uses US numbering by default.

The Even / Odd app for iPhone

A widget keeps the current week on your home screen. Free, offline, no ads.

Discover the app

Check a date → 2026 calendar →