Tool
What week number is it?
The current ISO 8601 week, plus a converter between any date and its week number.
Current week (ISO 8601)
Week 31
27 Jul 2026 – 2 Aug 2026 · 2026
Date → week number
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Week number → dates
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How week numbers work
The ISO 8601 week date system numbers the weeks of the year from 1 to 52 or 53. Weeks always start on Monday, and week 1 is defined as the week containing the year's first Thursday — the same as the week containing 4 January. A neat consequence is that the last days of December can fall in week 1 of the following year, and the first days of January can belong to the final week of the previous one, which is why this tool tracks a "week-year" separately from the calendar year. Week numbers are widely used in business, logistics and project planning across Europe, where "let's ship in week 32" is everyday shorthand. To see the live reference clock behind the calculation, visit UTC time now.
Frequently asked questions
- What week number is it now?
- It is currently ISO week 31 of 2026 (27 Jul 2026 to 2 Aug 2026). The clock and week update live on this page.
- How is the ISO week number calculated?
- Under ISO 8601, weeks start on Monday and week 1 is the week that contains the year's first Thursday — equivalently, the week containing 4 January. This means the first few days of January can belong to the last week of the previous year, and vice versa.
- Can a year have 53 weeks?
- Yes. Most years have 52 ISO weeks, but a year has 53 when it starts on a Thursday, or on a Wednesday in a leap year. 2026 has 53 weeks.
- Why do some calendars show a different week number?
- Not everyone uses ISO 8601. In the United States and some other countries, weeks often start on Sunday and week 1 is simply the week containing 1 January, which can give a different number. This tool uses the ISO standard, which is the norm in Europe and in business and software.