🗓️Week Number Calculator
ISO week number for any date.
About Week Number Calculator
Find the ISO 8601 week number and day of the year for any date. Useful for scheduling, reporting and project planning. Free online week number calculator.
🔒 Private by design — this tool runs entirely in your browser. Nothing you enter is uploaded to a server.
Frequently asked questions
Which week-numbering standard is used?＋
ISO 8601, where weeks start on Monday and week 1 contains the year's first Thursday. It also shows the day of the year.