🔢

Week Number Calculator

Find the ISO week number (1–53) for any date.

ISO 8601

The ISO week date system is used in business and logistics. Weeks always start on Monday.

Related Tools

🔯Days Between📆Day of Week📅Date Calculator📊Year at a Glance

Frequently Asked Questions

ISO 8601 week numbers run Monday to Sunday. Week 1 is the week containing the first Thursday.

The tool defaults to today and shows the current week number.

Most do. Some years have 53 ISO weeks.

About this calendar tool

Find the ISO week number for any date. What week of the year is it? It's built for a fast, no-fuss answer — enter your dates and the calculation happens instantly in your browser.

How to use Week Number Calculator

  1. Enter the dates or values into the fields above.
  2. Choose whether you want the result in days, weeks, months or years.
  3. The result updates instantly as you adjust the inputs.
  4. Try a different date range to compare two scenarios.

When this page is useful

Week Number Calculator is commonly used for: Working out exact timeframes for contracts, deadlines or planning. Settling an argument about how many days are left until something.

The result should be treated as a practical guide rather than professional advice. For legal, financial, health, tax, pregnancy, school holiday, tide or public holiday decisions, confirm important details with an official source or qualified professional.

Privacy and accuracy

MyCalendarTools tools run in your browser wherever possible. We aim to keep pages clear, lightweight and easy to read on mobile, tablet and desktop. If a page uses dates, public holidays or calendar rules, those rules can change over time, so checking the final result against the relevant authority is recommended for high-stakes decisions.

Canonical URL: https://mycalendartools.net/week-number/