Find the ISO week number and week-numbering year for a date.
The ISO week number uses a week containing the year's first Thursday as week one, so early January can belong to the previous year's final week. ISO 8601 weeks are the standard for business planning, reporting and manufacturing schedules.
ISO Week Number
ISO week from the Thursday rule: week 1 contains January 4
ISO week from the Thursday rule: week 1 contains January 4 The ISO week number uses a week containing the year's first Thursday as week one, so early January can belong to the previous year's final week.
ISO 8601 weeks are the standard for business planning, reporting and manufacturing schedules.
This calculator takes 3 inputs: Year, Month, Day. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.