All 53 ISO 8601 week numbers for 2026, each with its Monday-to-Sunday date range. Weeks start on Monday, and week 1 is the week containing the year's first Thursday.
| Week | Dates (Mon – Sun) | Month |
|---|---|---|
| Q1 2026 | ||
| 1 | 29 Dec 2025 – 4 Jan (starts in 2025) | January |
| 2 | 5 Jan – 11 Jan | January |
| 3 | 12 Jan – 18 Jan | January |
| 4 | 19 Jan – 25 Jan | January |
| 5 | 26 Jan – 1 Feb | January |
| 6 | 2 Feb – 8 Feb | February |
| 7 | 9 Feb – 15 Feb | February |
| 8 | 16 Feb – 22 Feb | February |
| 9 | 23 Feb – 1 Mar | February |
| 10 | 2 Mar – 8 Mar | March |
| 11 | 9 Mar – 15 Mar | March |
| 12 | 16 Mar – 22 Mar | March |
| 13 | 23 Mar – 29 Mar | March |
| Q2 2026 | ||
| 14 | 30 Mar – 5 Apr | April |
| 15 | 6 Apr – 12 Apr | April |
| 16 | 13 Apr – 19 Apr | April |
| 17 | 20 Apr – 26 Apr | April |
| 18 | 27 Apr – 3 May | April |
| 19 | 4 May – 10 May | May |
| 20 | 11 May – 17 May | May |
| 21 | 18 May – 24 May | May |
| 22 | 25 May – 31 May | May |
| 23 | 1 Jun – 7 Jun | June |
| 24 | 8 Jun – 14 Jun | June |
| 25 | 15 Jun – 21 Jun | June |
| 26 | 22 Jun – 28 Jun | June |
| Q3 2026 | ||
| 27 | 29 Jun – 5 Jul | July |
| 28 | 6 Jul – 12 Jul | July |
| 29 | 13 Jul – 19 Jul | July |
| 30 | 20 Jul – 26 Jul | July |
| 31 | 27 Jul – 2 Aug | July |
| 32 | 3 Aug – 9 Aug | August |
| 33 | 10 Aug – 16 Aug | August |
| 34 | 17 Aug – 23 Aug | August |
| 35 | 24 Aug – 30 Aug | August |
| 36 | 31 Aug – 6 Sep | September |
| 37 | 7 Sep – 13 Sep | September |
| 38 | 14 Sep – 20 Sep | September |
| 39 | 21 Sep – 27 Sep | September |
| Q4 2026 | ||
| 40 | 28 Sep – 4 Oct | October |
| 41 | 5 Oct – 11 Oct | October |
| 42 | 12 Oct – 18 Oct | October |
| 43 | 19 Oct – 25 Oct | October |
| 44 | 26 Oct – 1 Nov | October |
| 45 | 2 Nov – 8 Nov | November |
| 46 | 9 Nov – 15 Nov | November |
| 47 | 16 Nov – 22 Nov | November |
| 48 | 23 Nov – 29 Nov | November |
| 49 | 30 Nov – 6 Dec | December |
| 50 | 7 Dec – 13 Dec | December |
| 51 | 14 Dec – 20 Dec | December |
| 52 | 21 Dec – 27 Dec | December |
| 53 | 28 Dec – 3 Jan 2027 (ends in 2027) | December |
An ISO 8601 week number (sometimes written CW for "calendar week", or KW in German) identifies one of the 52 or 53 weeks of a year. Two rules define the system: every week starts on Monday, and week 1 is the week that contains the year's first Thursday — equivalently, the week containing January 4th. Businesses across Europe use week numbers for planning, scheduling, and reporting.
Most years have 52 ISO weeks, but a year has 53 when January 1st falls on a Thursday, or on a Wednesday in a leap year. 2026 starts on a Thursday, so it gets a 53rd week. Years like 2025 and 2027 have only 52. The extra week is why a "weekly" plan built around week numbers occasionally has to absorb a longer year. See the full list in how many weeks are in a year.
Because weeks are whole Monday-to-Sunday blocks, the first and last weeks of a year can spill over the calendar boundary. 2026's week 1 actually begins on 29 December 2025, and week 53 runs into January 2027. The few late-December or early-January days that land in a neighbouring year's week still belong, for ISO purposes, to that week's year.
This list is handy for scanning a whole year at a glance. To look up the week number for one exact date — or to count business days, work out a percentage, or check quarter progress — use the calculators on the week.hako.to home page.
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