How many weeks are in 2026?
2026 has 53 weeks in ISO 8601, because it starts on a Thursday. In the US system, where week 1 is the week of January 1 and partial weeks count, 2026 runs from week 1 to week 53. The last US week starts on Sunday, Dec 27, 2026.
ISO week 1 starts early, on Monday, Dec 29, 2025, because the week that holds January 1 also holds the first Thursday of 2026. The last ISO week, week 53, ends on Sunday, Jan 3, 2027.
US week 1 runs from Dec 28, 2025 to Jan 3, 2026. Because US weeks start on Sunday and ISO weeks on Monday, the same number never covers exactly the same days. For most of 2026, a date has the same number in both systems from Monday to Saturday, and the US number is one higher on Sundays.
Weeks month by month
January: US weeks 1 to 5; February: US weeks 6 to 9; March: US weeks 10 to 14; April: US weeks 14 to 18; May: US weeks 18 to 23; June: US weeks 23 to 27; July: US weeks 27 to 31; August: US weeks 31 to 36; September: US weeks 36 to 40; October: US weeks 40 to 44; November: US weeks 45 to 49; December: US weeks 49 to 53. In ISO numbering, January 2026 starts in week 1 and December ends in week 53.
2026 week numbers with dates
| Week | US (Sunday to Saturday) | ISO 8601 (Monday to Sunday) |
|---|---|---|
| 1 | Dec 28, 2025 to Jan 3 | Dec 29, 2025 to Jan 4 |
| 2 | Jan 4 to Jan 10 | Jan 5 to Jan 11 |
| 3 | Jan 11 to Jan 17 | Jan 12 to Jan 18 |
| 4 | Jan 18 to Jan 24 | Jan 19 to Jan 25 |
| 5 | Jan 25 to Jan 31 | Jan 26 to Feb 1 |
| 6 | Feb 1 to Feb 7 | Feb 2 to Feb 8 |
| 7 | Feb 8 to Feb 14 | Feb 9 to Feb 15 |
| 8 | Feb 15 to Feb 21 | Feb 16 to Feb 22 |
| 9 | Feb 22 to Feb 28 | Feb 23 to Mar 1 |
| 10 | Mar 1 to Mar 7 | Mar 2 to Mar 8 |
| 11 | Mar 8 to Mar 14 | Mar 9 to Mar 15 |
| 12 | Mar 15 to Mar 21 | Mar 16 to Mar 22 |
| 13 | Mar 22 to Mar 28 | Mar 23 to Mar 29 |
| 14 | Mar 29 to Apr 4 | Mar 30 to Apr 5 |
| 15 | Apr 5 to Apr 11 | Apr 6 to Apr 12 |
| 16 | Apr 12 to Apr 18 | Apr 13 to Apr 19 |
| 17 | Apr 19 to Apr 25 | Apr 20 to Apr 26 |
| 18 | Apr 26 to May 2 | Apr 27 to May 3 |
| 19 | May 3 to May 9 | May 4 to May 10 |
| 20 | May 10 to May 16 | May 11 to May 17 |
| 21 | May 17 to May 23 | May 18 to May 24 |
| 22 | May 24 to May 30 | May 25 to May 31 |
| 23 | May 31 to Jun 6 | Jun 1 to Jun 7 |
| 24 | Jun 7 to Jun 13 | Jun 8 to Jun 14 |
| 25 | Jun 14 to Jun 20 | Jun 15 to Jun 21 |
| 26 | Jun 21 to Jun 27 | Jun 22 to Jun 28 |
| 27 | Jun 28 to Jul 4 | Jun 29 to Jul 5 |
| 28 | Jul 5 to Jul 11 | Jul 6 to Jul 12 |
| 29 | Jul 12 to Jul 18 | Jul 13 to Jul 19 |
| 30 | Jul 19 to Jul 25 | Jul 20 to Jul 26 |
| 31 | Jul 26 to Aug 1 | Jul 27 to Aug 2 |
| 32 | Aug 2 to Aug 8 | Aug 3 to Aug 9 |
| 33 | Aug 9 to Aug 15 | Aug 10 to Aug 16 |
| 34 | Aug 16 to Aug 22 | Aug 17 to Aug 23 |
| 35 | Aug 23 to Aug 29 | Aug 24 to Aug 30 |
| 36 | Aug 30 to Sep 5 | Aug 31 to Sep 6 |
| 37 | Sep 6 to Sep 12 | Sep 7 to Sep 13 |
| 38 | Sep 13 to Sep 19 | Sep 14 to Sep 20 |
| 39 | Sep 20 to Sep 26 | Sep 21 to Sep 27 |
| 40 | Sep 27 to Oct 3 | Sep 28 to Oct 4 |
| 41 | Oct 4 to Oct 10 | Oct 5 to Oct 11 |
| 42 | Oct 11 to Oct 17 | Oct 12 to Oct 18 |
| 43 | Oct 18 to Oct 24 | Oct 19 to Oct 25 |
| 44 | Oct 25 to Oct 31 | Oct 26 to Nov 1 |
| 45 | Nov 1 to Nov 7 | Nov 2 to Nov 8 |
| 46 | Nov 8 to Nov 14 | Nov 9 to Nov 15 |
| 47 | Nov 15 to Nov 21 | Nov 16 to Nov 22 |
| 48 | Nov 22 to Nov 28 | Nov 23 to Nov 29 |
| 49 | Nov 29 to Dec 5 | Nov 30 to Dec 6 |
| 50 | Dec 6 to Dec 12 | Dec 7 to Dec 13 |
| 51 | Dec 13 to Dec 19 | Dec 14 to Dec 20 |
| 52 | Dec 20 to Dec 26 | Dec 21 to Dec 27 |
| 53 | Dec 27 to Jan 2, 2027 | Dec 28 to Jan 3, 2027 |
Holidays by week number in 2026
Federal holidays and Easter, with their week in each system. 1 of these 12 dates have a different number in the two systems, so say which one you mean when you plan around them. Falling on a weekend this year: Independence Day (Saturday, observed Fri, Jul 3).
| Holiday | Date | US week | ISO week |
|---|---|---|---|
| New Year’s Day | Thu, Jan 1 | 1 | 1 |
| Martin Luther King Jr. Day | Mon, Jan 19 | 4 | 4 |
| Presidents’ Day | Mon, Feb 16 | 8 | 8 |
| Easter Sunday | Sun, Apr 5 | 15 | 14 |
| Memorial Day | Mon, May 25 | 22 | 22 |
| Juneteenth | Fri, Jun 19 | 25 | 25 |
| Independence Day | Sat, Jul 4 (observed Fri, Jul 3) | 27 | 27 |
| Labor Day | Mon, Sep 7 | 37 | 37 |
| Columbus Day | Mon, Oct 12 | 42 | 42 |
| Veterans Day | Wed, Nov 11 | 46 | 46 |
| Thanksgiving | Thu, Nov 26 | 48 | 48 |
| Christmas Day | Fri, Dec 25 | 52 | 52 |
Writing a date as an ISO week date
ISO 8601 can also write a date as year, week and weekday. Thanksgiving 2026, Nov 26, 2026, becomes 2026-W48-4: week 48, day 4 (Thursday). Christmas Day becomes 2026-W52-5. Planning tools and some spreadsheets accept this form directly.
Other years: week numbers 2025 and week numbers 2027. For any single date, the week number tool gives the week in one tap, and the day of the week calculator tells you which weekday it falls on.