Week Number Calculator
Enter a date to find its ISO week number - the standard system used by businesses, schedules, and international standards.
Last updated: August 30, 2026
Frequently asked questions
What week number is June 15, 2024?
Week 24 of 2024, using the ISO 8601 standard where weeks start on Monday.
Why does ISO week numbering matter?
ISO 8601 week numbers are used widely in business, manufacturing, and international scheduling because they give every week a consistent, unambiguous number that doesn't reset awkwardly mid-week at year boundaries.
Does every year have exactly 52 weeks?
No - the ISO week-numbering system means most years have 52 weeks, but years where January 1 falls on a Thursday (or it's a leap year starting on Wednesday) get a 53rd week, since ISO weeks are defined by whole Monday-to-Sunday periods within the year.
Why do some calendars show week 53 for a year?
A year has 52 weeks plus one or two extra days, and under the ISO week-numbering standard, those leftover days sometimes form a 53rd week - this happens in years where January 1st falls on a Thursday, or in leap years where it falls on a Wednesday.
How many weeks are left this year?
Set the date above to today and check the "Full weeks left in year" figure - it counts complete 7-day weeks remaining between your chosen date and December 31.
What does 'week and year' mean together, like week 24 of 2024?
It's the standard way to unambiguously reference a specific week - the ISO week number alone can be shared between two different years near a year boundary, so pairing it with the ISO week year (shown above) removes that ambiguity.