Calendar & Dates
Week Number Calculator
Find the ISO week number for a date.
Open the tool to see results.
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How this tool works
ISO weeks start on Monday and week 1 is the week with the first Thursday.
All calculations run in your browser. No account is required, and this static version does not store your inputs.
Why can early January be week 52 or 53?
ISO week years do not always match calendar years.