Date & Time
Week Number Calculator
Find the ISO week number for any date. Free ISO 8601 week calculator.
Week 26
ISO week of 2026
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Frequently Asked Questions
Quick answers to common questions
How does this tool work?+
Uses the ISO 8601 standard where week 1 contains the first Thursday of the year.
Is this calculator free?+
Yes. 100% free with no signup. All calculations run in your browser.
Is my data private?+
Yes. Nothing is sent to any server.
Does it work on mobile?+
Yes. All date and time tools are mobile-friendly.