Get the week number of the year for a date.
Week of Year
Calculate which week of the year a specific date falls in.
How it works
This calculator uses the ISO 8601 standard for week numbering:
- Week 1 is the week containing the first Thursday of the year
- Weeks start on Monday
- A year can have 52 or 53 weeks
The calculator returns:
- Week Number: The week number (1-53)
- Year, Month, Day: The date components for reference
Use cases
- Project planning and tracking
- Business reporting (weekly reports)
- Academic calendars
- Payroll periods
- Production scheduling
- Statistical analysis by week
Examples
- January 1, 2025 → Week 1
- August 27, 2025 → Week 35
- December 31, 2025 → Week 1 (of 2026) or Week 53 (of 2025)
Note: Different countries and organizations may use different week numbering systems. This calculator follows the ISO 8601 international standard.