Week Number Calculator
See the ISO week number for any date, or find the dates of a given week.
ISO 8601: weeks start Monday; week 1 contains the year's first Thursday.
Week 46
2026 has 53 ISO weeks.
How are ISO week numbers defined?
How are ISO week numbers defined? In ISO 8601, weeks start on Monday and week 1 is the week containing the year's first Thursday. That means 1 January can fall in week 52 or 53 of the previous year, and some years have 53 weeks.
Features
- Current week shown on load
- Monday-to-Sunday date range
- Reverse lookup from week number to dates
- Number of weeks in the year
Good for
- Business and production planning
- School and payroll calendars
- Sprint planning
Frequently asked questions
Why does my calendar show a different week number?
Some calendars, often in the US, start weeks on Sunday and count 1 January as week 1. Timer Point uses the ISO standard, which is common in Europe and business software.
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