The ISO week number for today or any date you choose, with the date range of that week, the US-style week number and the day of the year.
Last updated: · By Furkan Çetinkaya · About & Methodology
ISO week number
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ISO 8601 weeks start on Monday, and week 1 is the week that contains the year's first Thursday. 2026 has 53 weeks, 2027 has 52.
| Week | 2026 | 2027 |
|---|---|---|
| 1 | Dec 29 – Jan 4 | Jan 4 – Jan 10 |
| 2 | Jan 5 – Jan 11 | Jan 11 – Jan 17 |
| 3 | Jan 12 – Jan 18 | Jan 18 – Jan 24 |
| 4 | Jan 19 – Jan 25 | Jan 25 – Jan 31 |
| 5 | Jan 26 – Feb 1 | Feb 1 – Feb 7 |
| 6 | Feb 2 – Feb 8 | Feb 8 – Feb 14 |
| 7 | Feb 9 – Feb 15 | Feb 15 – Feb 21 |
| 8 | Feb 16 – Feb 22 | Feb 22 – Feb 28 |
| 9 | Feb 23 – Mar 1 | Mar 1 – Mar 7 |
| 10 | Mar 2 – Mar 8 | Mar 8 – Mar 14 |
| 11 | Mar 9 – Mar 15 | Mar 15 – Mar 21 |
| 12 | Mar 16 – Mar 22 | Mar 22 – Mar 28 |
| 13 | Mar 23 – Mar 29 | Mar 29 – Apr 4 |
| 14 | Mar 30 – Apr 5 | Apr 5 – Apr 11 |
| 15 | Apr 6 – Apr 12 | Apr 12 – Apr 18 |
| 16 | Apr 13 – Apr 19 | Apr 19 – Apr 25 |
| 17 | Apr 20 – Apr 26 | Apr 26 – May 2 |
| 18 | Apr 27 – May 3 | May 3 – May 9 |
| 19 | May 4 – May 10 | May 10 – May 16 |
| 20 | May 11 – May 17 | May 17 – May 23 |
| 21 | May 18 – May 24 | May 24 – May 30 |
| 22 | May 25 – May 31 | May 31 – Jun 6 |
| 23 | Jun 1 – Jun 7 | Jun 7 – Jun 13 |
| 24 | Jun 8 – Jun 14 | Jun 14 – Jun 20 |
| 25 | Jun 15 – Jun 21 | Jun 21 – Jun 27 |
| 26 | Jun 22 – Jun 28 | Jun 28 – Jul 4 |
| 27 | Jun 29 – Jul 5 | Jul 5 – Jul 11 |
| 28 | Jul 6 – Jul 12 | Jul 12 – Jul 18 |
| 29 | Jul 13 – Jul 19 | Jul 19 – Jul 25 |
| 30 | Jul 20 – Jul 26 | Jul 26 – Aug 1 |
| 31 | Jul 27 – Aug 2 | Aug 2 – Aug 8 |
| 32 | Aug 3 – Aug 9 | Aug 9 – Aug 15 |
| 33 | Aug 10 – Aug 16 | Aug 16 – Aug 22 |
| 34 | Aug 17 – Aug 23 | Aug 23 – Aug 29 |
| 35 | Aug 24 – Aug 30 | Aug 30 – Sep 5 |
| 36 | Aug 31 – Sep 6 | Sep 6 – Sep 12 |
| 37 | Sep 7 – Sep 13 | Sep 13 – Sep 19 |
| 38 | Sep 14 – Sep 20 | Sep 20 – Sep 26 |
| 39 | Sep 21 – Sep 27 | Sep 27 – Oct 3 |
| 40 | Sep 28 – Oct 4 | Oct 4 – Oct 10 |
| 41 | Oct 5 – Oct 11 | Oct 11 – Oct 17 |
| 42 | Oct 12 – Oct 18 | Oct 18 – Oct 24 |
| 43 | Oct 19 – Oct 25 | Oct 25 – Oct 31 |
| 44 | Oct 26 – Nov 1 | Nov 1 – Nov 7 |
| 45 | Nov 2 – Nov 8 | Nov 8 – Nov 14 |
| 46 | Nov 9 – Nov 15 | Nov 15 – Nov 21 |
| 47 | Nov 16 – Nov 22 | Nov 22 – Nov 28 |
| 48 | Nov 23 – Nov 29 | Nov 29 – Dec 5 |
| 49 | Nov 30 – Dec 6 | Dec 6 – Dec 12 |
| 50 | Dec 7 – Dec 13 | Dec 13 – Dec 19 |
| 51 | Dec 14 – Dec 20 | Dec 20 – Dec 26 |
| 52 | Dec 21 – Dec 27 | Dec 27 – Jan 2 |
| 53 | Dec 28 – Jan 3 | — |
In the ISO 8601 system used in Europe and much of the world, weeks start on Monday and week 1 is the week with the year's first Thursday. Some years therefore have 53 weeks, and early January can belong to the previous year's last week.
In the US, weeks are usually counted from Sunday and week 1 is the week containing 1 January.
52 or 53 ISO weeks. A year has 53 weeks if it starts on a Thursday, or on a Wednesday in a leap year.
It probably uses the US system (weeks starting Sunday). Both numbers are shown above.