Week Number Calculator
Find the ISO 8601 week number, day of year, and weekday for any date.
Runs locally in your browser. Your input is not uploaded.
How to Use
- 1
Enter dates
One per line in YYYY-MM-DD format, e.g. 2026-07-12.
- 2
Results appear instantly
Each date shows its weekday, ISO week number, and day of year.
- 3
Copy what you need
Use the copy button to grab the whole report.
Frequently Asked Questions
- ISO 8601 numbers the weeks of a year 1–52 or 53, with weeks starting on Monday and week 1 being the week containing the first Thursday of January. This tool computes it exactly for any date.
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