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Week numbers

Look up the ISO 8601 week number for any date. 2026 has 53 weeks; the full table is below.

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How ISO week numbering works

In the ISO 8601 system used across Europe and in most planning software, weeks start on Monday and week 1 is the week containing the year's first Thursday. That means January 1 can belong to the last week of the previous year, and a year has 52 or 53 weeks. The United States more commonly numbers weeks from the week containing January 1 with Sunday starts, so US calendars can disagree with this table by one.

Week numbers for 2026

WeekMondaySunday
Week 1Dec 29, 2025Jan 4
Week 2Jan 5Jan 11
Week 3Jan 12Jan 18
Week 4Jan 19Jan 25
Week 5Jan 26Feb 1
Week 6Feb 2Feb 8
Week 7Feb 9Feb 15
Week 8Feb 16Feb 22
Week 9Feb 23Mar 1
Week 10Mar 2Mar 8
Week 11Mar 9Mar 15
Week 12Mar 16Mar 22
Week 13Mar 23Mar 29
Week 14Mar 30Apr 5
Week 15Apr 6Apr 12
Week 16Apr 13Apr 19
Week 17Apr 20Apr 26
Week 18Apr 27May 3
Week 19May 4May 10
Week 20May 11May 17
Week 21May 18May 24
Week 22May 25May 31
Week 23Jun 1Jun 7
Week 24Jun 8Jun 14
Week 25Jun 15Jun 21
Week 26Jun 22Jun 28
Week 27Jun 29Jul 5
Week 28Jul 6Jul 12
Week 29Jul 13Jul 19
Week 30Jul 20Jul 26
Week 31Jul 27Aug 2
Week 32Aug 3Aug 9
Week 33Aug 10Aug 16
Week 34Aug 17Aug 23
Week 35Aug 24Aug 30
Week 36Aug 31Sep 6
Week 37Sep 7Sep 13
Week 38Sep 14Sep 20
Week 39Sep 21Sep 27
Week 40Sep 28Oct 4
Week 41Oct 5Oct 11
Week 42Oct 12Oct 18
Week 43Oct 19Oct 25
Week 44Oct 26Nov 1
Week 45Nov 2Nov 8
Week 46Nov 9Nov 15
Week 47Nov 16Nov 22
Week 48Nov 23Nov 29
Week 49Nov 30Dec 6
Week 50Dec 7Dec 13
Week 51Dec 14Dec 20
Week 52Dec 21Dec 27
Week 53Dec 28Jan 3, 2027
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