Week Number Calculator
Calculate the ISO 8601 week number for any date, or find the date from a week number.
Week Number
Calculate the ISO 8601 week number
Result
Date:
09/01/2026
Friday
Week:
Week 2 of 2026
Day:
5. Friday
Weeks in Year:
53
Week Range:
05/01/2026 → 11/01/2026
ISO 8601 defines Week 1 as the week containing the first Thursday of the year. Weeks start on Monday.