📅 Week Number Calculator
Find the ISO week number for any date.
Week Number:
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How to Find the Week Number of a Date
Instantly determine the ISO week number (1-52 or 53) for any date. This tool is essential for project planning, payroll processing, and international business scheduling. It follows the ISO 8601 standard, where weeks start on Monday and Week 1 contains the first Thursday of the year.
Frequently Asked Questions
What is the ISO week number?
It’s an international standard (ISO 8601) for identifying weeks. Each week starts on Monday, and Week 1 is the week containing the first Thursday of January.
Why does the year sometimes differ from the calendar year?
If a date falls in early January but belongs to the last week of the previous year (or late December belonging to Week 1 of the next year), the ISO week year will adjust accordingly.
Is this calculator free and private?
Yes. It runs entirely in your browser with no data collection or server requests.
⚠️ Disclaimer
This calculator is provided for informational purposes only. Results are estimates and should not be considered legal, financial, or professional advice. Always verify important calculations with a qualified professional. DateCalcHub accepts no liability for decisions made based on these results.