What week is it?
It's week 40 of 2026
Mon, Sep 28 – Sun, Oct 4, 2026
Day 2 of 7 · 2026 has 53 ISO weeks
ISO and US week numbers
This is the ISO 8601 week number used across Europe and in most calendars: weeks start on Monday, and week 1 is the week with the year's first Thursday. In the US WEEKNUM system, where weeks start on Sunday and week 1 is the one containing January 1, today falls in week 40 of 2026.
Next week, week 41, runs Mon, Oct 5 – Sun, Oct 11, 2026.
In Excel or Google Sheets
- ISO week number
=ISOWEEKNUM(TODAY()) - US week number (Sunday start)
=WEEKNUM(TODAY())
Week pages
Week numbers by year
Frequently asked questions
What week number is it today?
Today, Tuesday, September 29, 2026, is in ISO week 40 of 2026 (Mon, Sep 28 – Sun, Oct 4, 2026).
How are ISO week numbers counted?
Weeks run Monday to Sunday. Week 1 is the week that contains the year's first Thursday (equivalently, January 4), so the first days of January can belong to the last week of the previous year.
How do I get the week number in Excel or Google Sheets?
Use =ISOWEEKNUM(TODAY()) for the ISO week. =WEEKNUM(TODAY()) gives the US-style number, which starts weeks on Sunday and counts the week containing January 1 as week 1.
How many weeks are in 2026?
2026 has 53 ISO weeks. Years have 53 when they start on a Thursday, or on a Wednesday in a leap year.