How do I use the Week Number Calculator?

Pick any date using the date picker. The week number updates instantly - no button needed. ISO weeks start on Monday, and Week 1 is the one that contains the year's first Thursday.

Is the Week Number Calculator free?

Yes, the Week Number Calculator on ToolHaven is completely free to use. No signup or registration is required.

Week Number Calculator

Pick any date and find out its ISO week number - the calendar week it falls in. Also shows the Monday-to-Sunday range for that week. Useful if you work with weekly reporting, sprints, or anything that references week numbers.

Select Date

Week 23

of 2026 · ISO 8601 Week Number

Week starts (Monday)

Monday, 1 Jun 2026

Week ends (Sunday)

Sunday, 7 Jun 2026

158

Day of Year

Quarter

Weeks in Year

How to use

Pick any date using the date picker.
The week number updates instantly - no button needed.
ISO weeks start on Monday, and Week 1 is the one that contains the year's first Thursday.

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