Why it matters
Project plans, manufacturing, and international business often schedule by week number rather than calendar month.
Use this calculator to find the ISO 8601 week number for a date, the week-year, and the Monday–Sunday range of that week.
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Pick a date to see its ISO week number.
ISO weeks start on Monday. Week 1 is the week with the year’s first Thursday.
What is an ISO week number?
The ISO 8601 week date system numbers weeks from 01 to 52 or 53. Weeks begin on Monday. Early January dates can belong to the previous ISO week-year, and late December dates can belong to the next.