All Tools VerseFind the ISO Week of the Year
Find the ISO 8601 week number for any date, with weeks starting on Monday.
- Runs in your browser
- Nothing uploaded
- Free, no sign-up
Calculated locally in your browser. Nothing is uploaded.
How to Use Find the ISO Week of the Year
- Pick a date. Any date you want the week for.
- Find the week. The ISO 8601 week number is worked out.
- Read the result. It shows the week and the ISO week year.
- Copy the result. Click Copy result. It all runs in your browser.
Frequently Asked Questions
Which week numbering is used?
ISO 8601, where weeks start on Monday and week 1 is the week containing the first Thursday of the year.
Why might the year differ?
Early January or late December dates can belong to a week in the neighbouring year, so the ISO week year is shown too.
Where is this used?
ISO week numbers are common in business planning, manufacturing, and many European calendars.
Is anything uploaded?
No. The calculation runs entirely in your browser, so nothing leaves the tab.
Is it free?
Yes. Every tool here is free to use with no sign up.
Related Tools
Find Date By Day of Year →
Convert between day-of-year (1-366) and calendar date - both directions, weekday, ISO ordinal, days…
Day of the Week Finder →
Find which day of the week any date falls on, for any year, in…
Find the Day of the Year →
Find the day-of-year number for any date, with the days remaining, leap years included.
Days Until New Year Counter →
Count the days from any date to the next New Year, with the weekday…
Calculate Date at Percent of Year →
Calculate Date at Percent of Year - Find the calendar date corresponding to any…
Check Common Year →
Check Common Year whether any year from 1 to 999999 is a common 365-day…
Check Leap Year →
Check whether a year is a leap year. Gregorian divisibility breakdown + nearest leap…
Age Difference Calculator →
Find the exact difference between two dates in years, months, and days, plus total…
Find Chinese Zodiac Sign →
Find your Chinese zodiac animal AND element (Wood/Fire/Earth/Metal/Water + Yang/Yin) for any year. Free,…
Find Christmas Day →
What weekday is Christmas? Dec 25 + Eve + NYE weekdays, leap-year, days-until, PTO…
Find Common Years →
List all common (365-day) and leap (366-day) years in a range. Counts, ratios, download.…
Easter Sunday Date Finder →
Find the date of Western (Gregorian) Easter Sunday for any year from 1583 onward.