Find the ISO week number (1–53) for any date.
ISO 8601 week numbers run Monday to Sunday. Week 1 is the week containing the first Thursday.
The tool defaults to today and shows the current week number.
Most do. Some years have 53 ISO weeks.
ISO 8601 numbers weeks from Monday to Sunday. Week 1 is the week containing the year's first Thursday, which means the first few days of January can belong to the previous ISO week-year and the final days of December can belong to the next one.
Week numbers are useful for manufacturing schedules, freight planning, project sprints, recurring reports, maintenance programs and international teams that refer to work by week rather than by date. For example, a supplier may request delivery in “week 42”; this tool lets you check which Monday-to-Sunday period that means for a particular year.
The ISO week-year does not always match the calendar year printed in the date. A date such as 1 January can still be part of the final ISO week of the previous year. Always read the week number and week-year as a pair when the date is close to the start or end of a year.
This page uses ISO 8601 week numbering. Some organisations use Sunday-start calendars, fiscal week systems, retail calendars or custom payroll periods, so their “week 1” may be different. Check the convention used by the organisation you are dealing with before relying on a week number for formal scheduling.