📆Calendar Tool

Week Number Calculator

Find the ISO week number for any date — and browse all weeks of the year.

Look up any date

ISO Week Number

Year2026

Week StartsApr 20, 2026

Week EndsApr 26, 2026

Day of Year111

2026

W02Jan 5 – Jan 11

W03Jan 12 – Jan 18

W04Jan 19 – Jan 25

W05Jan 26 – Feb 1

W06Feb 2 – Feb 8

W07Feb 9 – Feb 15

W08Feb 16 – Feb 22

W09Feb 23 – Mar 1

W10Mar 2 – Mar 8

W11Mar 9 – Mar 15

W12Mar 16 – Mar 22

W13Mar 23 – Mar 29

W14Mar 30 – Apr 5

W15Apr 6 – Apr 12

W16Apr 13 – Apr 19

W17Apr 20 – Apr 26← Now

W18Apr 27 – May 3

W19May 4 – May 10

W20May 11 – May 17

W21May 18 – May 24

W22May 25 – May 31

W23Jun 1 – Jun 7

W24Jun 8 – Jun 14

W25Jun 15 – Jun 21

W26Jun 22 – Jun 28

W27Jun 29 – Jul 5

W28Jul 6 – Jul 12

W29Jul 13 – Jul 19

W30Jul 20 – Jul 26

W31Jul 27 – Aug 2

W32Aug 3 – Aug 9

W33Aug 10 – Aug 16

W34Aug 17 – Aug 23

W35Aug 24 – Aug 30

W36Aug 31 – Sep 6

W37Sep 7 – Sep 13

W38Sep 14 – Sep 20

W39Sep 21 – Sep 27

W40Sep 28 – Oct 4

W41Oct 5 – Oct 11

W42Oct 12 – Oct 18

W43Oct 19 – Oct 25

W44Oct 26 – Nov 1

W45Nov 2 – Nov 8

W46Nov 9 – Nov 15

W47Nov 16 – Nov 22

W48Nov 23 – Nov 29

W49Nov 30 – Dec 6

W50Dec 7 – Dec 13

W51Dec 14 – Dec 20

W52Dec 21 – Dec 27

W53Dec 28 – Jan 3

How to Use the Week Number Calculator

1The current week number is shown automatically when you open the page.
2Select any date from the date picker to look up its week number.
3View the ISO week number, quarter, day of year, and full calendar details.
4The year is also shown — useful for dates near the turn of a year.

💡ISO week 1 is defined as the week containing the first Thursday of the year, which may fall in late December of the previous year.

Week Number FAQ

What is an ISO week number?

ISO week numbers follow the ISO 8601 standard: weeks start on Monday, and week 1 is the week containing the year's first Thursday.

How many weeks are in a year?

Most years have 52 weeks. Some years have 53 ISO weeks, which happens roughly every 5-6 years.

What week number is it today?

The calculator automatically shows the current week number when you load the page.