Week Number Calculator
Friday 7 August 2026 is in week 32 of 2026 under ISO 8601 numbering, and week 32 of 2026 under the US convention.
Today in UTC.
Weeks run Monday to Sunday. Week 1 holds the first Thursday.
Week number now
of 53 in 2026 · ISO 8601 numbering
Friday 7 August 2026 is in week 32 of 2026 under ISO 8601 numbering. That week runs from Monday 3 August 2026 to Sunday 9 August 2026.
Both conventions agree on this date: week 32 either way. They part company for most of January and often at the end of December.
Show the working
| Date | 2026-08-07 |
|---|---|
| Weekday | Friday |
| ISO week 1 starts | 2025-12-29 |
| US week 1 starts | 2025-12-28 |
| This week runs | 2026-08-03 to 2026-08-09 |
| Weeks in 2026 | 53 weeks |
ISO 8601 or US numbering
There are two ways to number the weeks of a year and they do not agree. Almost every tool that answers this question gives you one number without saying which one it used, and that is the whole reason people end up checking twice.
ISO 8601 is the international standard. Weeks run Monday to Sunday, and week 1 is the week that holds the first Thursday of the year. Put another way, week 1 is the first week with the majority of its days in the new year. This is what Europe uses, and what payroll, manufacturing, logistics and project software mean when they say "W32".
US numbering is simpler and looser. Weeks run Sunday to Saturday, and week 1 is just the week that holds 1 January, however few days of it fall in the new year. It turns up in American retail and broadcast calendars and in some academic terms.
If the system asking you for a week number does not say which it uses, ISO 8601 is the safer assumption. It is the standard, it is unambiguous, and it is what anything international will expect.
Why the two disagree in January
The disagreement is not a rounding quirk. It comes from the two rules answering different questions about the days that straddle New Year.
Take 1 January 2027. Under ISO it belongs to whichever week holds the first Thursday, which can put it in the last week of 2026. Under US numbering it is in week 1 of 2027 by definition, because week 1 is the week containing it. The same day, two numbers, both correct under their own rule.
This is why a week number quoted without its convention is not a complete answer, and why the result above always names the one it used and tells you when the other differs.
How many weeks are in a year
A year is 52 weeks and one day, or 52 weeks and two days in a leap year, because 365 does not divide by seven. That leftover is what makes the numbering conventions necessary in the first place.
Under ISO, 2026 holds 53 numbered weeks. A year holds 53 when it starts on a Thursday, or on a Wednesday in a leap year, and 52 otherwise. Under US numbering 2026 holds 53, because the part-weeks at either end are given numbers of their own.
The weeks around now
| Week | Starts, Monday | Ends, Sunday |
|---|---|---|
| Week 30 | 20 July 2026 | 26 July 2026 |
| Week 31 | 27 July 2026 | 2 August 2026 |
| Week 32, this week | 3 August 2026 | 9 August 2026 |
| Week 33 | 10 August 2026 | 16 August 2026 |
| Week 34 | 17 August 2026 | 23 August 2026 |
| Week 35 | 24 August 2026 | 30 August 2026 |
Frequently asked questions
What week of the year is it?
Week 32 of 2026 under ISO 8601, which is the numbering Europe and most business and payroll systems use. Under the US convention it is week 32. The tool above shows both and lets you switch.
What is the difference between ISO and US week numbers?
ISO 8601 weeks run Monday to Sunday, and week 1 is the week holding the first Thursday of the year. US weeks run Sunday to Saturday, and week 1 is simply the week holding 1 January. The two give different numbers for most of January and often for the last days of December.
How many weeks are in a year?
Fifty-two whole weeks and one day over, or two days over in a leap year, because 365 does not divide by 7. Under ISO numbering a year holds 52 or 53 numbered weeks: 2026 holds 53. Under US numbering it holds 53, because the part-weeks at each end are numbered too.
Which week number should I use?
Use the one the system asking for it uses. ISO 8601 is the international standard and the safe default for anything technical, financial or cross-border. US numbering turns up in American retail, broadcast and academic calendars. If a document does not say, ISO is the better assumption.
When does week 1 start?
Under ISO, week 1 of 2026 started on Monday 29 December 2025. Under the US convention it started on Sunday 28 December 2025. Both can begin in the previous December, which is normal and not an error.