Week Number Calculator

Find the ISO week number for any date.

ISO Week Number
Week 16
Thursday — Q2
106
Day of Year
259
Days Remaining
Q2
Quarter
365
Days in Year
2
Days to Weekend
4
Days to Monday
Year progress 29.0%
Quarter progress 16.2%
Leap year No
ISO week W16
US week W16
April 2026
Wk
Mon
Tue
Wed
Thu
Fri
Sat
Sun
14
1
2
3
4
5
15
6
7
8
9
10
11
12
16
13
14
15
16
17
18
19
17
20
21
22
23
24
25
26
18
27
28
29
30
All Weeks of 2026
W1 Dec 29 — Jan 4
W2 Jan 5 — Jan 11
W3 Jan 12 — Jan 18
W4 Jan 19 — Jan 25
W5 Jan 26 — Feb 1
W6 Feb 2 — Feb 8
W7 Feb 9 — Feb 15
W8 Feb 16 — Feb 22
W9 Feb 23 — Mar 1
W10 Mar 2 — Mar 8
W11 Mar 9 — Mar 15
W12 Mar 16 — Mar 22
W13 Mar 23 — Mar 29
W14 Mar 30 — Apr 5
W15 Apr 6 — Apr 12
W16 Apr 13 — Apr 19
W17 Apr 20 — Apr 26
W18 Apr 27 — May 3
W19 May 4 — May 10
W20 May 11 — May 17
W21 May 18 — May 24
W22 May 25 — May 31
W23 Jun 1 — Jun 7
W24 Jun 8 — Jun 14
W25 Jun 15 — Jun 21
W26 Jun 22 — Jun 28
W27 Jun 29 — Jul 5
W28 Jul 6 — Jul 12
W29 Jul 13 — Jul 19
W30 Jul 20 — Jul 26
W31 Jul 27 — Aug 2
W32 Aug 3 — Aug 9
W33 Aug 10 — Aug 16
W34 Aug 17 — Aug 23
W35 Aug 24 — Aug 30
W36 Aug 31 — Sep 6
W37 Sep 7 — Sep 13
W38 Sep 14 — Sep 20
W39 Sep 21 — Sep 27
W40 Sep 28 — Oct 4
W41 Oct 5 — Oct 11
W42 Oct 12 — Oct 18
W43 Oct 19 — Oct 25
W44 Oct 26 — Nov 1
W45 Nov 2 — Nov 8
W46 Nov 9 — Nov 15
W47 Nov 16 — Nov 22
W48 Nov 23 — Nov 29
W49 Nov 30 — Dec 6
W50 Dec 7 — Dec 13
W51 Dec 14 — Dec 20
W52 Dec 21 — Dec 27
W53 Dec 28 — Jan 3

Frequently Asked Questions

What is an ISO week number?

ISO 8601 defines week numbering: weeks start on Monday, and week 1 is the week containing the first Thursday of the year (or equivalently, the week containing January 4th). A year has 52 or 53 weeks. This standard is used internationally for business, logistics, and scheduling. The calculator uses ISO 8601 rules.

Can dates near year boundaries have surprising week numbers?

Yes — December 29-31 may belong to week 1 of the next year, and January 1-3 may belong to week 52 or 53 of the previous year. For example, January 1, 2024 (Monday) is in ISO week 1, but January 1, 2023 (Sunday) is in ISO week 52 of 2022. The calculator handles these edge cases correctly.

What is the current week number?

The calculator automatically shows today's ISO week number when you load the page. It also highlights the current week in the calendar view for quick reference. You can then select any other date to find its week number.

How many weeks are in a year?

Most years have 52 weeks. A year has 53 weeks if January 1 falls on a Thursday, or on a Wednesday in a leap year. Long years (53 weeks) occur roughly every 5-6 years. The calculator indicates whether the selected year has 52 or 53 ISO weeks.

How do I find all dates in a specific week?

Enter a year and week number, and the calculator shows all seven dates (Monday through Sunday) in that week. This is useful for planning, scheduling, and converting between "Week 14" style references and actual calendar dates.