What's the Current Week Number?
Check current week number using ISO-8601 rules and calculate week number for any date.
ISO Week Number Calculator
Check ISO week number and week-year for any date.
Current ISO week number
Week 8
ISO week year
2026
Week starts
Monday (ISO-8601)
ISO week 1 is the week containing the first Thursday of the year.
Weeks start on Monday in ISO-8601 week numbering.
ISO week numbers usually range from 1 to 52, and some years include week 53.
ISO week date format
YYYY-Www (e.g., 2026-W08)
Frequently asked questions
What is the current ISO week number?
It is the ISO-8601 week index for today, based on Monday-start weeks.
How is ISO week 1 defined?
Week 1 is the week containing the first Thursday of the year.
Do ISO weeks start on Sunday?
No. ISO weeks start on Monday.
Can an ISO year have week 53?
Yes. Some years include week 53 depending on calendar alignment.
Can week-year differ from calendar year?
Yes. Early January and late December can belong to adjacent ISO week-years.
What does YYYY-Www mean?
It is the ISO week date format: ISO week-year plus week number.
Can I check week number for another date?
Yes. Use the date picker or pass ?date=YYYY-MM-DD in the URL.