ganak.appWeek Number Calculator
Get the ISO week number for any date.
This calculator shows you the ISO week number for any date you select. ISO weeks follow a global standard where weeks start on Monday and week 1 is the week that contains the first Thursday of the year (or, equivalently, the week with January 4).
ISO week numbering is defined by the International Organization for Standardization (ISO), which ensures that week numbers are consistent across countries, calendars, and reporting systems.
You pick a date, and the tool instantly returns the corresponding week number and confirms that it uses the ISO week date system. This helps you align dates with week-based schedules, reports, and planning frameworks that rely on standardized week numbers.
- Project & Sprint Planning: Map deadlines, sprint cycles, and milestones to specific ISO week numbers.
- Reporting & Analytics: Align sales or performance reports to consistent week numbers for cleaner week-over-week comparisons.
- Payroll & Timesheets: Sync work logs and cycles to ISO-based weekly periods.
- Academic & Training Schedules: Organize curriculum or training blocks around week numbers instead of raw dates.
- Global Coordination: ISO week numbering removes ambiguity when coordinating across regions with different date formats.
Checking a Single Date
Selecting 3 December 2025 shows it falls in Week 49 of the ISO week calendar.
Planning a Sprint
If work is scheduled for week 12, you can quickly map ISO week 12 to the exact calendar dates.
Weekly Reporting
When preparing "Week 35 performance," you can confirm which dates fall inside ISO week 35.
Year-End Edge Cases
Dates near New Year may belong to the previous or next ISO year—this calculator resolves that automatically.