| Week 1 | December 29, 2025 – January 4, 2026 |
| Week 2 | January 5 – January 11, 2026 |
| Week 3 | January 12 – January 18, 2026 |
| Week 4 | January 19 – January 25, 2026 |
| Week 5 | January 26 – February 1, 2026 |
| Week 6 | February 2 – February 8, 2026 |
| Week 7 | February 9 – February 15, 2026 |
| Week 8 | February 16 – February 22, 2026 |
| Week 9 | February 23 – March 1, 2026 |
| Week 10 | March 2 – March 8, 2026 |
| Week 11 | March 9 – March 15, 2026 |
| Week 12 | March 16 – March 22, 2026 |
| Week 13 | March 23 – March 29, 2026 |
| Week 14 | March 30 – April 5, 2026 |
| Week 15 | April 6 – April 12, 2026 |
| Week 16 | April 13 – April 19, 2026 |
| Week 17 | April 20 – April 26, 2026 |
| Week 18 | April 27 – May 3, 2026 |
| Week 19 | May 4 – May 10, 2026 |
| Week 20 | May 11 – May 17, 2026 |
| Week 21 | May 18 – May 24, 2026 |
| Week 22 | May 25 – May 31, 2026 |
| Week 23 | June 1 – June 7, 2026 |
| Week 24 | June 8 – June 14, 2026 |
| Week 25 | June 15 – June 21, 2026 |
| Week 26 | June 22 – June 28, 2026 |
| Week 27 | June 29 – July 5, 2026 |
| Week 28 | July 6 – July 12, 2026 |
| Week 29 | July 13 – July 19, 2026 |
| Week 30 | July 20 – July 26, 2026 |
| Week 31 | July 27 – August 2, 2026 |
| Week 32 | August 3 – August 9, 2026 |
| Week 33 | August 10 – August 16, 2026 |
| Week 34 | August 17 – August 23, 2026 |
| Week 35 | August 24 – August 30, 2026 |
| Week 36 | August 31 – September 6, 2026 |
| Week 37 | September 7 – September 13, 2026 |
| Week 38 | September 14 – September 20, 2026 |
| Week 39 | September 21 – September 27, 2026 |
| Week 40 | September 28 – October 4, 2026 |
| Week 41 | October 5 – October 11, 2026 |
| Week 42 | October 12 – October 18, 2026 |
| Week 43 | October 19 – October 25, 2026 |
| Week 44 | October 26 – November 1, 2026 |
| Week 45 | November 2 – November 8, 2026 |
| Week 46 | November 9 – November 15, 2026 |
| Week 47 | November 16 – November 22, 2026 |
| Week 48 | November 23 – November 29, 2026 |
| Week 49 | November 30 – December 6, 2026 |
| Week 50 | December 7 – December 13, 2026 |
| Week 51 | December 14 – December 20, 2026 |
| Week 52 | December 21 – December 27, 2026 |
| Week 53 | December 28, 2026 – January 3, 2027 |
2026 has 53 ISO weeks. Most years have 52; a year has 53 when it starts on a Thursday (or on a Wednesday in a leap year).
Week 1 of 2026 starts on Monday, December 29, 2025 — ISO week 1 is the week containing the year's first Thursday, so it can start in late December.
It is currently week 30 of 53 in 2026 (today is Wednesday, July 22, 2026).
=ISOWEEKNUM(A1) returns the ISO week number of the date in A1 (the numbering used on this page); =WEEKNUM(A1) uses the US Sunday-start convention. Both work in Excel and Google Sheets.