Week Number Calculator
Find the ISO week number, day of year, quarter, and week date range for any date. Free online week number calculator.
When to Use
Use for payroll schedules, academic calendars, sprint planning, and reporting periods.
How to Use Week Number Calculator
- The current week number is shown automatically.
- Select any date to see its ISO week number.
- Also see the day of year, quarter, and whether the year is a leap year.
Examples
Today's week
Input: March 22, 2026
Output: Week 12 of 52
Frequently Asked Questions
What is an ISO week number?
ISO 8601 defines week 1 as the week containing the year's first Thursday. Weeks run Monday to Sunday.
How many weeks are in a year?
Most years have 52 ISO weeks. Some years have 53 weeks — 2026 has 53.