Week Number Calculator
Find the ISO week number for any date
How to Use
Enter a date. Click Calculate to find the ISO week number and year.
Frequently Asked Questions
What is ISO week numbering?
ISO 8601 defines weeks starting on Monday, with week 1 containing the first Thursday of the year.
Can a year have 53 weeks?
Yes, years starting on Thursday (or Wednesday in leap years) have 53 weeks per ISO 8601.