Week Number Finder
Find the ISO and US week number for any date.
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How to Find the Week Number of Any Date
Whether you're planning a project, scheduling a meeting, or just curious, knowing the exact week number of the year is essential. Our Week Number Finder provides instant, accurate calculations for both the US system and the international ISO-8601 standard.
Why Are There Different Week Numbers?
It can be confusing when different calendars show different week numbers. Here's why:
- ISO-8601 (International): The week starts on Monday. The first week of the year is the one that contains at least 4 days of the new year (or contains the first Thursday of January). This is the standard used in Europe and by many international businesses.
- US System: The week starts on Sunday. The first week of the year is the one containing January 1st. This is commonly used in the United States, Canada, and Australia.
How to Use This Tool
- Select a Date: Click on the date input field to open the calendar picker.
- Choose Your Date: Select any day, month, and year you want to check.
- Get Results: Click "Find Week Number" to instantly see the USA Week, ISO Week, and the Day of the Year.
Features
- Dual System Support: See both US and ISO week numbers side-by-side.
- Day of Year: Find out exactly which day of the year (1-366) a date falls on.
- Mobile Friendly: Works perfectly on your phone or desktop.
Frequently Asked Questions (FAQ)
What is the current week number?
The current week number depends on the system used (ISO-8601 vs. US). Our tool calculates both instantly based on today's date.
What is an ISO week number?
The ISO-8601 standard defines weeks starting on Monday. The first week of the year is the one containing the first Thursday of January.
How is the US week number different?
In the US system, weeks typically start on Sunday. The first week of the year is the one containing January 1st.
How do I calculate the day of the year?
The day of the year (1-365 or 366 for leap years) represents the number of days elapsed since January 1st. Our tool provides this automatically.
Is this tool free to use?
Yes, the Week Number Finder is completely free and works directly in your browser without any downloads.