ISO Week Number Calculator - Free, Instant, In Your Browser
Enter a date to find its ISO 8601 week number (weeks start Monday, week 1 contains the year's first Thursday).
How to use ISO Week Number Calculator
- 1Enter the required date(s) and details above.
- 2Click Calculate - ISO Week Number Calculator runs instantly, right in your browser.
- 3Read your result below.
Your file is processed in your browser and is never uploaded.
Frequently Asked Questions
How is this calculated?
Using a standard, well-established algorithm - see the description above for the specific method and its accuracy.
Is my data sent to a server?
No - everything runs entirely in your browser with JavaScript. Nothing is uploaded.