ISO Week Number Calculator

ISO Week Number Calculator

The ISO Week Number Calculator converts any date into its ISO 8601 week number, week-year, and Monday-to-Sunday range. It also works in reverse, turning a week-year and week number back into exact dates, and shows a full-year calendar of every ISO week. Because ISO 8601 numbering has subtle edge cases around week 53 and the year boundary, this tool gives you instant, verifiable answers for scheduling, payroll, sprint planning, and reporting.

Nutzung

Pick any date to instantly see its ISO week number, ISO week-year, and the Monday and Sunday that bound that week. Use the Previous week, This week, and Next week buttons to step through the calendar, or click any row in the full-year week list to jump straight to it. To go the other way, enter a week-year and a week number in the reverse section to get the exact start and end dates for that ISO week.

Funktionen

• Date to ISO week – Get the week number, ISO week-year, day of week, and day of year for any date.
• Week range – See the Monday start and Sunday end dates for the selected week.
• Reverse lookup – Convert a week-year plus week number back into an exact date range, with validation for week 53.
• Quick navigation – Jump to the previous week, next week, or today with a single click.
• Full-year calendar – Browse every ISO week of the year with the current week highlighted.
• Edge-case accurate – Correctly handles 53-week years and dates that fall into the previous or next ISO week-year.