The Week Number Calculator tells you which ISO 8601 week a date falls in. Pick a date and it shows the week number and ISO year, plus the day of the year, the quarter, the weekday and how many days remain in the year.
ISO week numbers explained
The ISO 8601 standard numbers weeks starting on Monday, with week 1 containing the year's first Thursday. This calculator applies that standard exactly, so the result matches business and European conventions.
Alongside the week number it shows the day of the year, the calendar quarter and the weekday for quick reference.
Useful for
- Business and fiscal week reporting
- Project and sprint planning
- Logistics and scheduling
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