How Many Weeks in a Year
See whether a year has 52 weeks plus leftover days, and when the ISO calendar has 53 weeks.
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How to use this calculator
Enter a calendar year to see how many days it has, how that splits into 52 weeks plus leftover days, and whether the ISO week calendar has 52 or 53 weeks. The table below compares nearby years so you can spot 53-week years quickly.
Frequently asked questions
How many weeks are in a year?
A common year has 365 days = 52 weeks and 1 day. A leap year has 366 days = 52 weeks and 2 days. That leftover is why New Year's Day moves one or two weekdays each year.
When does a year have 53 ISO weeks?
An ISO year has 53 weeks when December 28 falls in week 53, typically when January 1 is a Thursday, or a Wednesday in a leap year.
Is 52 weeks exactly one year?
No. 52 × 7 = 364 days, so every year has at least one extra day beyond 52 full weeks.
Does leap year change the week count?
Leap years add a second leftover day (52 weeks + 2 days) and can also produce a 53-week ISO year more often than common years.