Week Number Calculator
Find the current week number, or the week number for any date. ISO 8601 week numbering.
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Week Number
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ISO Week
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Day of Year
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Day of Week
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Year Progress
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Weeks Remaining
Frequently Asked Questions
What is the ISO week number?
ISO 8601 defines week 1 as the week containing the first Thursday of the year. Weeks start on Monday. Most of the world uses this standard.
What week of the year is it right now?
Use this calculator with today's date to find the current week number. The year has 52 or 53 weeks.
Why do some years have 53 weeks?
A year has 53 ISO weeks when January 1 is a Thursday (or Wednesday/Thursday in a leap year). This happens roughly every 5-6 years.