Week Number Calculator
Find the week number of the year for any date.
Quick answer: Pick a date to see its week number. For example January 1, 2026 is ISO week 1 and December 31, 2026 is ISO week 53.
Dates are worked out from your own device's calendar day. Nothing is sent anywhere.
How to use it
- Pick a date.
- The ISO week number appears, with the US week number beside it.
- Below, you see the Monday to Sunday dates of that week.
What people use it for
- Planning and scheduling
- Homework and school
- Work and deadlines
- Travel and events
- Curiosity
Questions
How do I find the week number of a date?
Pick the date here. The calculator uses the ISO 8601 rule: weeks start on Monday and week 1 contains the first Thursday.
Can a date in January belong to week 52 or 53?
Yes. Early January days can belong to the last week of the previous ISO year.
Is it free?
Yes. No sign-up, no install and no limit.
Is anything saved or sent?
No. Everything runs in your browser. Only your own best score, where a page shows one, is kept on your device.
Last updated 2026-10-24. Free to use, no sign-up. Made by ficklestudio26.