Tools

ISO Week Number Calculator by Date

Find the ISO week number and week year for any date.

Week Number Calculator

Get the ISO week number for a given date, including the week year. This helps with reporting, sprint planning, and calendar alignment.

How to use the Week Number Calculator

  1. Select a date.
  2. Click Calculate.
  3. Copy the week number result.

Common use cases

  • Planning sprints by ISO week.
  • Aligning reports to week numbers.
  • Comparing weekly metrics.
  • Building calendar-based filters.

Tips & notes

  • ISO weeks differ from simple calendar weeks.
  • Check week year near January 1 and December 31.
  • Use ISO Week Converter for reverse lookup.

Related time tools

  • ISO Week Converter
  • Month Calendar Generator
  • Quarter Calculator

FAQ

Which standard is used?
ISO 8601 week numbering.
Do weeks start on Monday?
Yes. ISO weeks start on Monday.
Why is the week year different?
ISO week years can differ near year boundaries.